const maxn = 20 ;
const maxm = 30020 ;
var A:array [ 1 .. maxn , 1 .. maxm ] of longint;
    lenA : array [ 1 .. maxn ] of longint ;
    Prefix : array [ 1 .. maxn, 1..maxm ] of longint ;
    match : array [ 1 .. maxn, 1 .. maxn ] of longint ;
    vertexLabel : array [ 1 .. maxn ] of longint ;
    edgeCost : array [ 1 .. maxn, 1 .. maxn ] of longint ;
    n , i, j, k, t , numVertices, numVertexSet : longint ;
    value, maxValue : longint ;
    maxHamPathCost : array [ 1 .. maxn , 0 .. 1 shl maxn ] of longint ;
    notPart : array [ 1.. maxn ] of boolean ;
    io : text ;
    ch : char ;
    notFound : boolean ;
begin
  assign ( io , 'adn.in' ) ;
  reset ( io ) ;
  readln ( io, n ) ;
  for i := 1 to n do
  begin
    lenA [ i ] := 0 ;
    while not ( eoln ( io ) or eof ( io ) ) do
    begin
      read ( io, ch ) ;
      lenA [ i ] := lenA [ i ] + 1 ;
      A [ i , lenA [ i ] ] := longint (ch) ;
    end ;
    readln ( io ) ;
  end ;
  close ( io ) ;
  for i := 1 to n do
  begin
    Prefix [ i , 1 ] := 0 ;
    k := 0 ;
    for j := 2 to lenA [ i ] do
    begin
      while ( 0 < k ) and ( A [ i , 1 + k ] <> A [ i , j ] ) do
      begin
        k := Prefix [ i , k ] ;
      end ;
      if ( A [ i , 1 + k ] = A [ i , j ] ) then
      begin
        k := k + 1 ;
      end ;
      Prefix [ i , j ] := k ;
    end ;
  end ;
  for i := 1 to n do
  begin
    notPart [ i ] := true ;
  end ;
  for i := 1 to n do
  begin
    j := 1 ;
    while ( j <= n ) and notPart [ i ] do
    begin
      if ( i <> j ) and notPart [ j ] then
      begin
        k := 0 ;
        t := 1 ;
        while ( t <= lenA [ j ] ) and notPart [ i ] do
        begin
          while ( 0 < k ) and ( A [ i , 1 + k ] <> A [ j , t ] ) do
          begin
            k := Prefix [ i , k ] ;
          end ;
          if ( A [ i , 1 + k ] = A [ j , t ] ) then
          begin
            k := k + 1 ;
          end ;
          if ( lenA [ i ] = k ) then
          begin
            notPart [ i ] := false ;
            k := k - 1 ;
          end ;
          t := t + 1 ;
        end ;
        if notPart [ i ] then
        begin
          match [ j , i ] := k ;
        end ;
      end ;
      j := j + 1 ;
    end ;
  end ;
  numVertices := 0 ;
  for i := 1 to n do
  begin
    if notPart [ i ] then
    begin
      numVertices := numVertices + 1 ;
      vertexLabel [ numVertices ] := i ;
    end ;
  end ;
  for i := 1 to numVertices do
  begin
    for j := 1 to numVertices do
    begin
      edgeCost [ i , j ] := match [ vertexLabel [ i ] , vertexLabel [ j ] ] ;
    end ;
  end ;
  numVertexSet := 1 shl numVertices ;
  for i := 1 to numVertexSet - 1 do
  begin
    for j := 1 to numVertices do
    begin
      if ( 0 <> ( i and ( 1 shl ( j-1 ) ) ) ) then
      begin
        maxValue := 0 ;
        for t := 1 to numVertices do
        begin
          if ( j <> t ) and ( 0 <> ( i and ( 1 shl ( t - 1 ) ) ) ) then
          begin
            value := edgeCost [ j , t ] + maxHamPathCost [ t , i and ( not ( 1 shl ( j - 1 ) ) ) ] ;
            if ( maxValue < value ) then
            begin
              maxValue := value ;
            end ;
          end ;
        end ;
        maxHamPathCost [ j , i ] := maxValue ;
      end ;
    end ;
  end ;
  assign ( io , 'adn.out' ) ;
  rewrite ( io ) ;
  if ( 0 = n ) then
  begin
    writeln ( io , '' ) ;
  end else
  begin
    i := numVertexSet - 1 ;
    j := 1 ;
    for t := 2 to numVertices do
    begin
      if ( maxHamPathCost [ j ] [ i ] < maxHamPathCost [ t ] [ i ] ) then
      begin
        j := t ;
      end ;
    end ;
    for k := 1 to lenA [ vertexLabel [ j ] ] do
    begin
      write ( io, char ( A [ vertexLabel [ j ] , k ] ) ) ;
    end ;
    i := i and ( not ( 1 shl ( j - 1 ) ) ) ;
    while ( 0 <> i ) do
    begin
      notFound := true ;
      t := 1 ;
      while notFound do
      begin
        if ( j <> t ) and ( 0 <> ( i and ( 1 shl ( t - 1 ) ) ) ) and
           ( maxHamPathCost [ j , i or ( 1 shl ( j - 1 ) ) ] =
             edgeCost [ j ] [ t ] + maxHamPathCost [ t , i ] ) then
        begin
          notFound := false ;
        end else
          t := t + 1 ;
        begin
        end ;
      end ;
      for k := edgeCost [ j , t ] + 1 to lenA [ vertexLabel [ t ] ] do
      begin
        write ( io , char ( A [ vertexLabel [ t ] , k ] ) ) ;
      end ;
      j := t ;
      i := i and ( not ( 1 shl ( j - 1 ) ) );
    end ;
  end ;
  close ( io ) ;
end.
const maxn = 20 ;
const maxm = 30020 ;
var A : array [ 1 .. maxn , 1 .. maxm ] of longint ;
    lenA : array [ 1 .. maxn ] of longint ;
    Prefix : array [ 1 .. maxn, 1..maxm ] of longint ;
    match : array [ 1 .. maxn, 1 .. maxn ] of longint ;
    vertexLabel : array [ 1 .. maxn ] of longint ;
    edgeCost : array [ 1 .. maxn, 1 .. maxn ] of longint ;
    n , i, j, k, t , numVertices, numVertexSet : longint ;
    value, maxValue : longint ;
    maxHamPathCost : array [ 1 .. maxn , 0 .. 1 shl maxn ] of longint ;
    notPart : array [ 1.. maxn ] of boolean ;
    io : text ;
    ch : char ;
    notFound : boolean ;
begin
  assign ( io , 'adn.in' ) ;
  reset ( io ) ;
  readln ( io, n ) ;
  for i := 1 to n do
  begin
    lenA [ i ] := 0 ;
    while not ( eoln ( io ) or eof ( io ) ) do
    begin
      read ( io, ch ) ;
      lenA [ i ] := lenA [ i ] + 1 ;
      A [ i , lenA [ i ] ] := longint (ch) ;
    end ;
    readln ( io ) ;
  end ;
  close ( io ) ;
  for i := 1 to n do
  begin
    Prefix [ i , 1 ] := 0 ;
    k := 0 ;
    for j := 2 to lenA [ i ] do
    begin
      while ( 0 < k ) and ( A [ i , 1 + k ] <> A [ i , j ] ) do
      begin
        k := Prefix [ i , k ] ;
      end ;
      if ( A [ i , 1 + k ] = A [ i , j ] ) then
      begin
        k := k + 1 ;
      end ;
      Prefix [ i , j ] := k ;
    end ;
  end ;
  for i := 1 to n do
  begin
    notPart [ i ] := true ;
  end ;
  for i := 1 to n do
  begin
    j := 1 ;
    while ( j <= n ) and notPart [ i ] do
    begin
      if ( i <> j ) and notPart [ j ] then
      begin
        k := 0 ;
        t := 1 ;
        while ( t <= lenA [ j ] ) and notPart [ i ] do
        begin
          while ( 0 < k ) and ( A [ i , 1 + k ] <> A [ j , t ] ) do
          begin
            k := Prefix [ i , k ] ;
          end ;
          if ( A [ i , 1 + k ] = A [ j , t ] ) then
          begin
            k := k + 1 ;
          end ;
          if ( lenA [ i ] = k ) then
          begin
            notPart [ i ] := false ;
            k := k - 1 ;
          end ;
          t := t + 1 ;
        end ;
        if notPart [ i ] then
        begin
          match [ j , i ] := k ;
        end ;
      end ;
      j := j + 1 ;
    end ;
  end ;
  numVertices := 0 ;
  for i := 1 to n do
  begin
    if notPart [ i ] then
    begin
      numVertices := numVertices + 1 ;
      vertexLabel [ numVertices ] := i ;
    end ;
  end ;
  for i := 1 to numVertices do
  begin
    for j := 1 to numVertices do
    begin
      edgeCost [ i , j ] := match [ vertexLabel [ i ] , vertexLabel [ j ] ] ;
    end ;
  end ;
  numVertexSet := 1 shl numVertices ;
  for i := 1 to numVertexSet - 1 do
  begin
    for j := 1 to numVertices do
    begin
      if ( 0 <> ( i and ( 1 shl ( j-1 ) ) ) ) then
      begin
        maxValue := 0 ;
        for t := 1 to numVertices do
        begin
          if ( j <> t ) and ( 0 <> ( i and ( 1 shl ( t - 1 ) ) ) ) then
          begin
            value := edgeCost [ j , t ] + maxHamPathCost [ t , i and ( not ( 1 shl ( j - 1 ) ) ) ] ;
            if ( maxValue < value ) then
            begin
              maxValue := value ;
            end ;
          end ;
        end ;
        maxHamPathCost [ j , i ] := maxValue ;
      end ;
    end ;
  end ;
  assign ( io , 'adn.out' ) ;
  rewrite ( io ) ;
  if ( 0 = n ) then
  begin
    writeln ( io , '' ) ;
  end else
  begin
    i := numVertexSet - 1 ;
    j := 1 ;
    for t := 2 to numVertices do
    begin
      if ( maxHamPathCost [ j ] [ i ] < maxHamPathCost [ t ] [ i ] ) then
      begin
        j := t ;
      end ;
    end ;
    for k := 1 to lenA [ vertexLabel [ j ] ] do
    begin
      write ( io, char ( A [ vertexLabel [ j ] , k ] ) ) ;
    end ;
    i := i and ( not ( 1 shl ( j - 1 ) ) ) ;
    while ( 0 <> i ) do
    begin
      notFound := true ;
      t := 1 ;
      while notFound do
      begin
        if ( j <> t ) and ( 0 <> ( i and ( 1 shl ( t - 1 ) ) ) ) and
           ( maxHamPathCost [ j , i or ( 1 shl ( j - 1 ) ) ] =
             edgeCost [ j ] [ t ] + maxHamPathCost [ t , i ] ) then
        begin
          notFound := false ;
        end else
          t := t + 1 ;
        begin
        end ;
      end ;
      for k := edgeCost [ j , t ] + 1 to lenA [ vertexLabel [ t ] ] do
      begin
        write ( io , char ( A [ vertexLabel [ t ] , k ] ) ) ;
      end ;
      j := t ;
      i := i and ( not ( 1 shl ( j - 1 ) ) );
    end ;
  end ;
  close ( io ) ;
end.