#include <iostream>
using namespace std;

int euclid(int n, int m) {
    if (m == 1) {
        return n;
    }
    if (0 == (n % m)) {
        return m;
    } else {
        return euclid(m, n % m);
    }
}

int main(void) {
    int n;
    cin >> n;
    if (0 == (n % 2)) {
        cout << n / 2 << endl;
    } else {
        cout << euclid(n, (n-1)/2) << endl;
    }
    return 0;
}