#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("factorial.in");
ofstream fout("factorial.out");

int factorial(int n)
{
    // single line to find factorial
    return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}


// Driver code
int main()
{
    int num;

    fin>>num;
    fout<< factorial(num) << endl;
    return 0;
}