program Factorial;

var input: Word;

function Fact (n: word): NativeUInt;
begin
  case n of
    0: Fact := 0;
    1: Fact := 1;
    else Fact := n * Fact(n - 1)
  end;
end;


begin
  Write('Which Factorial to calculate? ');
  ReadLn(input);

  WriteLn(Fact(input));
end.