#include <algorithm>
#include <iostream>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <list>
#include <cmath>
#include <stack>
#include <string>
#include <cstring>
#include <numeric>
#include <iomanip>
#include <fstream>
using namespace std;
const long long inf=1e9+7;
const long long mod=1e9+7;
const int64_t CYCLES_PER_SEC=2800000000;
//
inline uint32_t Xor128(){
	static uint32_t x=123456789;
	static uint32_t y=362436069;
	static uint32_t z=521288629;
	static uint32_t w=88675123;
	uint32_t t=x^(x<<11);
	x=y;y=z;z=w;
	return w=(w^(w>>19))^(t^(t>>8));
}
struct Timer{
	int64_t start;
	Timer(){reset();}
	void reset(){start=getcycle();}
	void plus(double a){start-=(a*CYCLES_PER_SEC);}
	inline double get(){return (double)(getcycle()-start)/CYCLES_PER_SEC;}
	inline int64_t getcycle(){
		uint32_t low,high;
		__asm__ volatile ("rdtsc":"=a"(low),"=d"(high));
		return ((int64_t)low)|((int64_t)high<<32);
	}
};
//
int n;
long long p[100000];
int sum(long long hoge){
	int s=0;
	while(hoge>0){
		s+=hoge%10;
		hoge/=10;
	}
	return s;
}
int main(){
	cin>>n;
	if(n==0){
		cout<<0<<endl;
		return 0;
	}
	long long ans=1;
	for(int i=0;i<n;i++){
		cin>>p[i];
		while(p[i]>=10){
			p[i]=sum(p[i]);
		}
		ans*=p[i];
		while(ans>=10){
			ans=sum(ans);
		}
	}
	cout<<ans<<endl;
	return 0;
}