#include <iostream>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <string>
#include <map>
#include <queue>
#define ll long long

int main() {
  ll N;
  std::cin >> N;
  ll ss = sqrt(N)+1;
  ll ans = -1;
  for(ll i = 3; i <= ss; i++) {
    if(N % i == 0) {
      ans = i;
      break;
    }
  }
  if(ans == -1) {
    ans = N;
  }
  std::cout << ans << std::endl;
}