#include<iostream>
#include<fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int factorial(int n)
{
    if(n==0) return 1;
    else
    {
        return factorial(n-1);
    }


}
int main()
{
    int n;
fin>>n;
fout<<factorial(n);

    return 0;
}