#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD=1000000007;
#define INF 1LL<<30
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()

int main() {
    double n,k;
    cin>>n>>k;
    double ans=n/2;
    cout<<setprecision(10)<<ans<<endl;
}