#include <iostream>
using namespace std;
int main()
{
	long long n, a[100000], sum = 0;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		long long int x;
		cin >> x;
		sum += x;
	}
	long long ans = 0;
	while (true)
	{
		long long x = 0;
		ans = sum;
		if (sum < 10) {

			break;
		}
		while (ans != 0) {
			x += ans % 10;
			ans /= 10;
		}
		sum = x;
		
	}
	cout << sum;
}