program Project2;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Math;

function Fact(N: Integer): Integer;
begin
       if N < 0 then Result := -1
  else if N = 0 then Result :=  1
  else               Result :=  N * Fact(N-1);
end;

function GetUniqueChars(S: String): String;
var
  UniqueChars: array of Char;
  CS: Integer;
begin
  if Length(S) > 1 then
  begin
    UniqueChars := '';

    for CS := 1 to Length(S) do
      {TODO}
  end
  else
    UniqueChars := S;

  Result := UniqueChars;
end;

var
  N: Integer;
  S: String;

begin
try
  {$I-}
  Readln(N);
  {$I+}

  if IOResult <> 0 then
  begin
    Writeln('Error! Please enter something more understandable next time...');
    Readln;
    Exit;
  end;

  N := Fact(N);

  if N = -1 then
  begin

    Writeln(
      'The correct value for the factorial function ' +
      'is a non-negative integer.'
    );

    Readln;
    Exit;

  end;

  if N <= 0 then
  begin
    Writeln('Out of Boundaries Error!');
    Readln;
    Exit;
  end;

  S := IntToStr(N);
  //S := GetUniqueChars(S);
  Writeln(S);
  Readln;
except
  raise;
end;
end.