#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<bitset>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#include<list>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<functional>
#include<cstdio>
#include<cstdlib>
using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define INF 2e9
//#define MOD 1000000007
#define MOD 998244353
#define LINF (long long)4e18
#define jck 3.141592

const double EPS = 1e-10;

using ll = long long;
using Pi = pair<int,int>;
using Pl = pair<ll,ll>;

int main(){
    int N; cin >> N;
    vector<ll> P(N);
    rep(i,N) cin >> P[i];
    ll tmp = 1;
    rep(i,N){
        string k = to_string(P[i]);
        int m = k.size();
        int now = 0;
        rep(j,m){
            now += k[j]-'0';
        }
        tmp *= now;
    }
    string t = to_string(tmp);
    while(true){
        int s = t.size();
        int now = 0;
        rep(i,s){
            now += t[i]-'0';
        }
        t = to_string(now);
        if(t.size() == 1) break;
    }
    cout << t << endl;
}