#include <iostream>
using namespace std;
int isPrime(int num){
    int itr;
    for(itr=2;itr<=num/2;itr++){
        if(num%itr==0)
           return 0;
    }
    return 1;
}
void fun(int num){
     if(isPrime(num))
      return num;
}



int main(){
    int num;
    cin>>num;
    cout<<fun(num);
 

}