Contest1390/1390J.cpp

#include<bits/stdc++.h>

using namespace std;

int main() {
    int n;
    while (cin >> n) {
        int s = 1;
        for (int k = n; k >= 2; k -= 2) {
            s *= k;
        }
        cout << s << endl;
    }
    return 0;
}