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

long long f(long long N)
{
    std::vector<long long> prim;
    for (long long n = 3; n < (N / n); n++) {
        for (long long m = 0; m < prim.size(); m++) {
            if ((n % prim[m]) == 0) goto is_prim;
        }
        if ((N % n) == 0) return n;
        prim.push_back(n);
    is_prim:
        ;
    }
    return N;
}

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