#include<iostream>
using namespace std ;
int main(){
    int n ;
    cin>>n;
    if(n<=0){
        cout<<"Invalid input";
        return 0;
    }
    int i=2,largest=-1;
    while(n>1)
    {
        if(n%i==0){
            largest = i;
        
        while (n%i == 0){
            n/=i;
        }
        }
    }
    i++;
if(largest==-1){
    cout<<"No prime factors found";
}
else{
    cout<<largest;
}
}