const
  n = 20;
var
  a:array[1..n] of integer;
  i, j:integer;
  check:boolean;
begin
  for i := 1 to n do
  begin
    repeat
      a[i] := random(21);
      check := true;
      for j := 1 to i - 1 do
        if a[i] = a[j] then
        begin
          check := false;
          break;
        end;
    until check;
    write(a[i], ' ');
  end;
  writeln;
end.