// cout << "Case #" << test << ": ";
#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
typedef long long ll;
#define MOD 1000000007
using namespace std;
int main() {
    ll n, k;
    cin >> n >> k;
    cout << n / 2.0 << endl;
}