#include<stdio.h>
#include<stdbool.h>
#include<math.h>

bool isPrime(unsigned long);
int main(void){
	unsigned long n, div = 3;
	
	scanf("%lu\n", &n);
	if(isPrime(n)){
		printf("%lu\n", n);
	}else{
		while(n%div != 0){
			div++;
		}
		printf("%lu\n", div);
	}
	return 0;
}

bool isPrime(unsigned long x){
	unsigned long root = sqrt(x);
	unsigned long div;
	for(div = 2; div <= root ; div++){
		if(x%div == 0){
			return 0;
		}else{
			continue;
		}
	}
	return true;
}