// I SELL YOU...! 
#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<queue>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
ll val(ll n){
  ll res=0;
  while(n>0){
    res += n%10;
    n/=10;
  }
  return res;
}
signed main(){
  ll n,v;
  cin >> n;
  ll p[n];
  for(int i=0;i<n;i++){
    cin >> p[i];
    if(i==0){
      v = p[i];
      while(v>=10){
        v = val(v);
      }
    }else{
      v *= p[i];
      while(v>=10){
        v = val(v);
      }
    }
  }
  cout << v << endl;
}