#include<iostream>
#include<vector>
#include<math.h>
#include<algorithm>
#include<string>
using namespace std;

typedef long long ll;

ll sumofdigits(ll x){
	ll ans=0;
	while(x){
		ans+=(x%10);
		x/=10;
	}
	return ans;
}

int main(){
	int n;
	cin>>n;
	vector<ll>p(n);
	for(int i=0;i<n;i++){
		cin>>p[i];
		while(p[i]>10){
		 	p[i]=sumofdigits(p[i]);
		}
	}
	ll tmp=1;
	for(int i=0;i<n;i++){
		tmp*=p[i];
	}
	while(tmp>=10){
		tmp=sumofdigits(tmp);
	}
	cout<<tmp<<endl;
	return 0;
}