#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstdio>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdlib>
#include <cstdio>
using namespace std;

#define next '\n'
#define rep(i, n) for(int (i) = (0); (i) < (n); (i++))
using ll = long long;
using ull = unsigned long long;

int countDigit(int n){
    int ans = 1;
    while(n / 10 != 0){
        n /= 10;
        ans++;
    }

    return ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n; cin >> n;
    ll num = 1;
    rep(i, n){
        ll p; cin >> p;
        num *= p;
    }

//    cout << num << next;

    ull length = countDigit(num);

    ull ans = num;
    ull x = num;

    while(length != 1){
        ull sum = 0;
        for(int i = 0; i < length; i++){
            sum += x % 10;
            x /= 10;
        }
        
        length = countDigit(sum);
        ans = sum;
        x = sum;
    }

    cout << ans << next;
}