#include <iostream>
#include <vector>
#include <string.h>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	int N,i;
	cin>>N;
	vector<LL> P(N);
	for (i=0;i<N;i++){
		cin>>P[i];
	}
	LL X=P[0];
	char S[100];
	string S1;
	for (i=1;i<N;i++){
		X*=P[i];
		sprintf(S,"%lld",X);
		S1=S;
		int Y=0;
		for (int j=0;j<S1.length();j++){
			Y+=S1[j]-'0';
		}
		X=Y;
	}
	while (X>9){
		sprintf(S,"%lld",X);
		S1=S;
		int Y=0;
		for (int j=0;j<S1.length();j++){
			Y+=S1[j]-'0';
		}
		X=Y;
	}
	cout<<X<<endl;
	return 0;
}