#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n;
    cin >> n;

    ll ans = 1;

    rep(i,n){
        ll tmp = 0;
        ll x; cin >> x;
        rep(j,20){
            tmp += x % 10;
            x /= 10;
        }
        ans *= tmp;
        tmp = 0;
        rep(j,20){
            tmp += ans % 10;
            ans /= 10;
        }
        ans = tmp;
    }
    while(ans >= 10){
        ll tmp = 0;
        rep(i,20){
            tmp += ans % 10;
            ans /= 10;
        }
        ans = tmp;
    }
    cout << ans << endl;
    return 0;
}