#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
const int INF = 1000000001;
const float PI = 3.14;
typedef map<string, int> msi;
typedef vector<pair<int, int> > vii;
typedef priority_queue<pair<int, int>, vector<pair<int, int> >,
                       greater<pair<int, int> > >
    pq;
vector<pair<int, int> >::iterator iter;
int main(int argc, char* argv[]) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  cout << n / 2 << endl;
  return 0;
}
