#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, a;
  cin >> N;
  if (N % 2 == 0) {
    cout << N / 2 << "\n";
  } else if (N % 2 == 1) {
    a = N / 2;
    cout << a + 1 << "/n";
  }
}
