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

template<typename T> int SumDigit(T N) {
	int res = 0;
	while(N > 0) { res += (N % 10); N /= 10; }
	return res;
}

int main(){
    int N;
    cin >> N;
    long long ans = 1;
    vector<long long> A(N);
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        A[i] = SumDigit(A[i]);
        //A[i] = SumDigit(A[i]);
        ans *= A[i];
    }

    while (to_string(ans).length() > 1) {
        ans = SumDigit(ans);
    }
    cout << ans << endl;
    return 0;
}