#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(int)(n); i++)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;


int main() {
  int n, k; cin >> n >> k;
  double ans = (n+1)*n/2.0 / (n+1);
  cout << fixed << setprecision(6);
  cout << ans << endl;
}