#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    int n;cin >>n;
    vector<ll> p(n);
    ll mult =1;
    for(int i=0;i<n;i++){
        cin >> p[i];
        mult*=p[i];
    }
    ll dig=0;
    ll sum=0;
    while(mult>9){
        while(mult>0){
            dig=mult%10;
            sum += dig;
            mult/=10; 
        }
        mult=sum;
    }
    cout << mult <<endl;
}