#include<bits/stdc++.h>
using namespace std;
int main(){
int n;
cin>>n;
if(n%2==0){
cout<<"2"<<endl;
}
if(n%3==0){
cout<<"3"<<endl;
}
if(n%5==0){
cout<<"5"<<endl;
}
if(n%7==0){
cout<<"7"<<endl;
}
return 0;
}