#include <iostream>
using namespace std;
int main() {
    int n;
    cin >> n;
    if ( n <= 0 ) {
        cout << "Invalid input";
        return 0;
    } 
    if ( n == 1)
        cout << "No prime factors found";
        return 0;
    }
    int largest = -1;
    
    while (n % 2 == 0) {
        largest = 2;
        n /= 2;
    }
    for (int i = 3; i *i <= n; i += 2)
    {
        while (n % i == 0) {
            largest = i;
            n /= i;
        }
    }
    if (n > 2) {
    largest = n;
    }
    if (largest == -1)
    cout << "No prime factors found";
    else 
    cout << largest;
    return 0;
    
}