#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

int getCountZero(int number, int sys) {
    int count = 0;
    while (number / sys > 0) {
        if (number % sys == 0) {
            count++;
        }
        number /= sys;
    }
    return count;
}

int getIsPrime(int n) {
    for (int i = 2; i<sqrt(n); i++) {
    if (n % i == 0) {
        return false;
    }
}
return true;
}

int main() {
    int number = 0;
    cin >> number;
    int maxSys = 2;
    for(int i = 2; i <= number; i++) {
       if (getCountZero(number, i) > getCountZero(number, maxSys)) {
           if (getIsPrime(i)) {
            maxSys = i;
           }
       }
    }
    cout << maxSys;
    return 0;
}