#include <iostream>
using namespace std;

bool isPrime(long long x){
   if(!(x & 1)) return false;
   for(long long i = 3;i * i <= x;i += 2) if(!(x % i)) return false;
   return true;
}

int main(){
   long long n;
   cin >> n;
   if(isPrime(n)){
      cout << n << endl;
      return 0;
   }
   if(!(n & 1) && isPrime(n / 2)){
      cout << n / 2 << endl;
      return 0;
   }
   for(int i = 3;i * i <= n;i++){
      if(n % i == 0){
         cout << i << endl;
         return 0;
      }
   }
   cout << 4 << endl;
}