inform.pas

program project1;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes, Crt;

{$R *.res}

type
  data = record
    letter: char;
    count: integer;
  end;

Var
  a: array [1..1000] of data;
  temp: data;
  c: char;
  i,j,n: integer;
begin
  ClrScr;
  n:=0;
  Read(c);
  While c<>'.' do
    begin
      Inc(n);
      a[n].letter:=c;
      a[n].count:=1;
      Read(c);
    end;
  Writeln;

  For i:=1 to n do
    begin
      For j:=i+1 to n do
        if a[i].letter=a[j].letter
          then
            Inc(a[i].count);
    end;

  For i:=1 to n-1 do
    For j:=1 to n-i do
      If a[j].letter>a[j+1].letter
        then
          begin
            temp:=a[j];
            a[j]:=a[j+1];
            a[j+1]:=temp;
          end;

  For i:=1 to n-1 do
    For j:=1 to n-i do
      If a[j].count<a[j+1].count
        then
          begin
            temp:=a[j];
            a[j]:=a[j+1];
            a[j+1]:=temp;
          end;

  For i:=1 to n do
    begin
      For j:=i+1 to n do
        if a[i].letter=a[j].letter
          then
            a[j].count:=0;
      If a[i].count<>0
        then
          Write(a[i].letter);
    end;
  ReadLn;
end.