#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
// #include <boost/multiprecision/cpp_int.hpp>

// namespace mp = boost::multiprecision;

using namespace std;

// #define big mp:cpp_int
#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

string yn(bool f){return f?"Yes":"No";}
string YN(bool f){return f?"YES":"NO";}



signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	int N;
	int sum = 1;
	int x = 1;
	
	cin>>N;
	
	for(int i = 0; i < N; i++){
		int P;
		int temp = 0;
		
		cin>>P;
		
		x *= P;
		
		while(P > 0){
			temp += P%10;
			P /= 10;
		}
		
		sum *= temp;
	}
	
	int temp = 0, temp2 = 0;
	
	while(sum >= 10){
		temp = 0;
		
		while(sum > 0){
				temp += sum%10;
				sum /= 10;
		}
		sum = temp;
	}
	
	
	
	cout<<temp<<endl;
	// cout<<temp2<<endl;
	
	return 0;
}