#include<bits/stdc++.h>
using namespace std;
 
#define rep(i, a, n) for(int i=a; i<n; i++)
#define ll long long
#define all(x) begin(x), end(x)
#define toInt(x) (x - '0')
#define pll pair<ll, ll>
#define pli pair<ll, int>

const long long INF = 1LL<<60;
const int inf = 1 << 30;
const int mod = 1e9+7;


template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

const int MAX = 5000;
int main(){
  int n, k;
  cin >> n >> k;

  cout << (long double)(n+1) * n /(2 * ((n+1))) << endl;
}