#include <bits/stdc++.h>
using namespace std;

int main() {
    int64_t n;
    cin >> n;
    for (int64_t i = 3; i * i <= n; i++)
        if (n % i == 0) {
            cout << i;
            return 0;
        }
    if (n & 1)
        cout << n << endl;
    else
        cout << n / 2 << endl;
    return 0;
}