#include <iostream>
using namespace std;

const int TEN = 10;

int main() {
    int n;
    cin >> n;
    while (n >= TEN) {
        int result = 1, copyN = n;
        while (copyN > 0) {
            int digit = copyN % TEN;
            result *= digit;
            copyN /= TEN;
        }
        n = result;
    }
    cout << n;
    return 0;
}