#include<iostream>
using namespace std;
int N;
int F=0;
long T=1;
main()
{
	cin>>N;
	for(int i=0;i<N;i++)
	{
		long A;cin>>A;
		if(F==0&&(A>=9||T>=9||A*T>=9))F=1;
		if(A==0)F=-1;
		T=A%9*T%9;
	}
	cout<<(T?T:F==1?9:0)<<endl;
}