#include <iostream>
#include <vector>
#include <algorithm>

long long f(long long N)
{
    long long n, m, mod;
    for (n = 3; (N / n) > 2; n += mod) {
        mod = N % n;
        if (mod == 0) {
            return n;
        }
    }
    for (m = n; (N / m) > 1; m += n) {
        if ((N % (m + mod)) == 0) {
            return (m + mod);
        }
    }
    return N;
}

int main()
{
    long long N;
    std::cin >> N;
    std::cout << f(N) << std::endl;
    return 0;
}