#include<iostream>
#include<algorithm>
#include<vector>
#include<functional>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<cstdio>
#include<numeric>
using namespace std;
using ll = long long;
int main(){
  ll n, k;
  cin >> n >> k;
  printf("%.10f\n", (double)n / 2.0);
  return 0;
}