var f:text;
    ok:boolean;
    i,j,q,p,n:longint;
begin
     assign(f,'fact.in');
     reset(f);
              read(f,p);
     close(f);
     i:=1;
     j:=5;
     ok:=true;
     while i<=p do
     begin
          q:=j;
          while q mod 5=0 do
          begin
               q:=q div 5;
               inc(i);
               if (i=p)and(q mod 5=0) then
                  ok:=false;
          end;
          j:=j+5;
     end;
     assign(f,'fact.out');
     rewrite(f);
     if ok=false then
        write(f,-1)
     else
         if j=5 then
            write(f,1)
         else
         write(f,j-5);
     close(f);
end.