//#define _GLIBCXX_DEBUG
#include "bits/stdc++.h"

using namespace std;

//------------------------------- Type Names -------------------------------//

using i64 = int_fast64_t;

using seika = string;
//{akari : 1D, yukari : 2D, maki : 3D} vector
template <class kizuna>
using akari = vector<kizuna>;
template <class yuzuki>
using yukari = akari<akari<yuzuki>>;
template <class tsurumaki>
using maki = akari<yukari<tsurumaki>>;
//{akane : ascending order, aoi : decending order} priority queue
template <class kotonoha>
using akane = priority_queue<kotonoha, akari<kotonoha>, greater<kotonoha>>;
template <class kotonoha>
using aoi = priority_queue<kotonoha>;
//------------------------------- Libraries --------------------------------//

//------------------------------- Dubug Functions ---------------------------//
inline void print()
{
    cout << endl;
}
template <typename First, typename... Rest>
void print(const First &first, const Rest &... rest)
{
    cout << first << ' ';
    print(rest...);
}
//------------------------------- Solver ------------------------------------//

void solve()
{
    int n;
    cin >> n;
    i64 ans, p;
    cin >> ans;
    auto dig = [](i64 x) {
        i64 res = 0;
        while (x)
        {
            res += x % 10;
            x /= 10;
        }
        return res;
    };
    ans = dig(ans);
    for (int i = 1; i < n; i++)
    {
        cin >> p;
        ans *= dig(p);
        ans = dig(ans);
    }
    while (ans > 9)
    {
        ans = dig(ans);
    }
    cout << ans << endl;
}

int main()
{
    solve();
    return 0;
}