#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;

int main() {
    int N, K;
    cin >> N >> K;
    double ans = 0;
    for (int i = 0; i <= N; ++i) {
        ans += ((double)i) / ((double) (N+1));
    }

    cout << fixed << setprecision(6) << ans << endl;


    return 0;
}