#include <iostream>

using namespace std;

unsigned long long t[21] = {0, 1, 2, 6, 24, 120,720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000};
int main(void){
    int n;
    cin >> n;
    cout << t[n] << endl;
    return 0;
}