#pragma region
#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define VPII vector<PII>
#define VPLL vector<PLL>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
#pragma endregion
//-------------------
int main() {
    cin.tie(0); ios::sync_with_stdio(false); //cout << fixed << setprecision(15);
    int n; cin >> n;
    ll ans = 1;
    auto f = [](ll x) {
        ll res = 0;
        while(x) {
            res += x%10;
            x /= 10;
        }
        return res;
    };
    FOR(i,0,n-1) {
        ll p; cin >> p;
        ans *= p;
        while(ans >= 10) {
            ans = f(ans);
        }
    }
    cout << ans << endl;
    return 0;
}