program fact;
var n2,n5,nn,i,p,n,aux:longint;
    fin,fout:text;
    ok:boolean;
{*---------MAIN-----------------*}
begin
  assign(fin,'fact.in');
  assign(fout,'fact.out');
  reset(fin);
  rewrite(fout);
  readln(fin,p);
  ok:=true;
  n:=0;
  while ok do
    begin
      inc(n);
      n2:=0;
      n5:=0;
      for i:=1 to n do
        begin
          aux:=i;
          while aux mod 2 = 0 do
            begin
              inc(n2);
              aux := aux div 2;
            end;
          while aux mod 5 = 0 do
            begin
              inc(n5);
              aux := aux div 5;
            end;
        end;
      nn:=n2;
      if n5 < n2 then nn:=n5;
      if nn = p then
        begin
          writeln(fout,n);
          ok:=false;
        end;
      if nn >p then
        begin
          writeln(fout,-1);
          ok:=false;
        end;
    end;
  close(fout);
end.