#include<iostream>
#include<algorithm>
using namespace std;

bool a(int x)
{
    for(int i = 2; i <= x - 1; i++)
    {
        if(x % i == 0)
        {
            return false;
        }
    }
    return true;
}
int main()
{
    int maxn = -1000;
    int n;
    cin >> n;
    for(int i = 2; i <= n - 1; i++)
    {
        int maxm = -100;
        if(n % i == 0 && a(i) && a(n / i))
        {
            maxm = max(maxm, n / i);
            maxn = max(maxm, maxn);
        }
    }
    cout << maxn << endl;
    return 0;
}