#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef pair<int, int> P;
typedef long long ll;
ll culc(ll a){
    while(a>=10){
        ll tmp = 0;
        string s = to_string(a);
        for(auto i:s){
            tmp+=(i-'0');
        }
        a = tmp;
    }
    return a;
}
int main(){
    int n;
    cin >> n;
    ll res = 1;
    rep(i,n){
        ll p;
        cin >> p;
        res = culc(res*p);
    }
    cout << res << endl;
    return 0;
}