#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    cin.tie(0)->sync_with_stdio(0);

    ll N, K;
    cin >> N >> K;

    double ans = N / 2.0;
    printf("%.10f\n", ans);

    return 0;
}