#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    int p[n];
    long total = 1;
    for(int i = 0; i < n; i++) {
        cin >> p[i];
        total *= p[i];
    }
    auto f = [&] (long c) {
    	int digit = 0;
    	while(c > 0) {
    		digit += c % 10;
    		c = c / 10;
    	}
    	return digit;
    };
    while(total > 9) {
    	total = f(total);
    }
    cout << total << endl;
}