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


int main() {

	
	int n=0,sum=0,a[100],num=0;
	cin >>n;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		sum = sum + a[i]; 
	}
	if (sum < 10)
	{
		cout << sum;
		return 0;
	}
	
	while (sum!=0) {
		num = num+(sum%10);
		sum = sum / 10;
		
		//num = num + sum;
		if (sum == 0 && num>=10)
		{
			
			sum = num;
			num = 0;
		}

		
	}
	cout << num;
	



}