#include<iostream>
#include <algorithm>
#include<cstdio>
#include<string>
#include<math.h>
#include<vector>
#include <queue>
#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
#define srep(i,s,t) for (long long i = s; i < t; i++)
#define drep(i,n) for(int i = (n)-1; i >= 0; i--)
#define mod 1000000007
using namespace std;
typedef vector<vector<char>> field_t;

typedef pair<int, int> point_t;



int main()
{
    long long N,i,K;
	double Z;
    cin >> N >> K;
	Z=0;
	rep(i,N+1){
		Z=Z+double(i)/(N+1);
	}
	cout<<fixed<<setprecision(1)<<Z<<endl;

}