#include <iostream>
#include <fstream>
using namespace std;

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

int main()
{
    long N, f = 1;
    fin>>N;
    if (N == 0 || N == 1)
        fout<<1;
    else
    {
        while (N)
        {
            f *= N;
            N--;
        }
        fout<<f;
    }
    fin.close();
    fout.close();
    return 0;
}