#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define ll long long
#define INF 1000000000000000000

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    vector<ll> A(N);
    rep(i, N) { cin >> A[i]; }

    ll MOD = pow(10, 9);
    ll a = 1, b = 0;
    rep(i, N) {
        a *= A[i];
        if (a >= MOD)
            b += a / MOD;
        a %= MOD;
    }

    ll ans = 0;
    string first;
    string aa = to_string(a), bb = to_string(b);
    first = bb + aa;
    while (1) {
        rep(i, first.size()) { ans += first[i] - '0'; }

        if (ans < 10) {
            cout << ans << endl;
            return 0;
        }

        first = to_string(ans);
        ans = 0;
    }

    return 0;
}