#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
using namespace std;
typedef  long long int lint;
typedef pair<int, int> P;
typedef pair<lint, lint> LLP;
#define rep(i, n) for (int i = 0; i < n; i++)
#define repr(i, n) for (int i = n; i >= 0; i--)
#define sort(v) sort((v).begin(), (v).end())
#define reverse(v) reverse((v).begin(), (v).end())
/*
vector<char>al(26);
al = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
vector<char>AL(26);
AL = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
*/

int main() {
	int N;
	cin >> N;
	vector<lint>P(N);
	rep(i, N) {
		cin >> P[i];
	}
	lint p = 0;
	rep(i, N) {
		while (P[i] >= 10) {
			while (P[i] != 0) {
				p += P[i] % 10;
				P[i] /= 10;
			}
			P[i] = p;
			p = 0;
		}
	}
	lint ans = 1;
	rep(i, N) {
		ans *= P[i];
	}
	while (ans >= 10) {
		while (ans != 0) {
			p += ans % 10;
			ans /= 10;
		}
		ans = p;
		p = 0;
	}
	cout << ans << endl;
}