#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==1)
 {
    return 1;
 }   
 else {
    return n*factorial(n-1);
 }

}