/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.05.13 11:52:48
**/
#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    double n,k;cin >> n >> k;
    cout << n/2 << endl;
    return 0;
}