const N=50;
type TChastot=array [1..N] of byte;

var inStr,outStr:string; chast:TChastot;
    i,j:integer;  maxChast,iPos:integer;

begin
  readln(inStr);
  for i:=1 to length(inStr) do
  begin
    chast[i]:=0;
    for j:=i to length(inStr) do
      if inStr[i]=inStr[j] then
        chast[i]:=chast[i]+1;
  end;
  maxChast:=Low(integer); iPos:=0;
  for i:=1 to length(inStr) do
    if maxChast<chast[i] then
    begin
     maxChast:=chast[i];
     iPos:=i;
    end;
  i:=iPos; outStr:='';
  while (i<=length(inStr)) and (chast[i]=chast[iPos]) do
  begin
   outStr:=outStr+inStr[i];
   i:=i+1;
  end;
  if length(outStr)<length(inStr) then
  begin
   i:=pos(outStr,copy(inStr,length(outStr)+1,length(inStr)-length(outStr)));
   while i=0 do
   begin
    delete(outStr,length(outStr),1);
    i:=pos(outStr,copy(inStr,length(outStr)+1,length(inStr)-length(outStr)));
   end;
  end;
  writeln(outStr);
end.

Edited by author 14.12.2011 02:20