#include<bits/stdc++.h>
using namespace std;

long jiecheng(int n) {//返回值需要为long,否则13之后的数会因为结果过大而溢出
    if (n == 0 || n == 1) {
        return 1;
    } else {
        return n * jiecheng(n - 1);
    }
}
int main() {
    int n;
    cin >> n;
    long result = jiecheng(n);
    cout << result;
}