#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;

int main(){

    long double N;
    cin >> N;
    cout << fixed << setprecision(18) << (N-4) * (N-3) * (N-2) * (N - 1) * N/715231440.0 << endl;

    return 0;
}