#include<bits/stdc++.h>
using namespace std;
int main(){
	int a;
	cin>>a;
	if(a%2==0) 
		cout<<"2"<<endl;
	if(a%3==0) 
		cout<<"3"<<endl;		
	if(a%5==0) 
		cout<<"5"<<endl;
	if(a%7==0) 
		cout<<"7";
	
}
/**************************************************************
	Problem: 1299
	User: tonghuawei
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/