#include <bits/stdc++.h>
#define REP(i, start, end) for (int64_t i=start, i##Len=(end); i < i##Len; ++i)
#define REPR(i, start, end) for (int64_t i=start, i##Len=(end); i > i##Len; --i)
using ll = int64_t;
using namespace std;


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);

    ll N, K;
    cin >> N >> K;
    cout << double(N * (N+1) / 2) / double(N+1) << endl;

}