#include<bits/stdc++.h> 
using namespace std;
typedef long long ll;
template<typename T1,typename T2> bool chmin(T1 &a,T2 b){if(a<=b)return 0; a=b; return 1;}
template<typename T1,typename T2> bool chmax(T1 &a,T2 b){if(a>=b)return 0; a=b; return 1;}
 

 
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);
 
    long double n,k;
    cin>>n>>k;
    long double ans = n/2.0;
    cout << ans << endl;
 
}