#include <iostream>
#include <vector>

using namespace std;

int main() {
	int n;
	cin >> n;
	long long total = 0;
	for (int i = 0; i < n; i++) {
		long long t;
		cin >> t;
		total += t;
	}

	while (total / 10 != 0) {
		long long sum = 0;
		while (total != 0) {
			sum += (total % 10);
			total = total / 10;
		}

		total = sum;
	}
	
	cout << total << endl;
	return 0;
}