#include <iostream>
using namespace std;

long long factorial(int n);

int main() {

    int n;
    cin >> n;

    cout << factorial(n) << endl;

    return 0;
}

long long factorial(int n) {

    // write your code here......
    if (n == 0 || n == 1)
        return 1;
    else
        return n * factorial(n - 1);

}