import java.util.*;
import java.io.*;

class Main{
	public static int transform(String txt) {
		int len=txt.length();
		int Ans=0;
		for(int i=0;i<len;i++) {
			Ans+=Character.getNumericValue(txt.charAt(i));
		}
		if(Ans<10) {
			return Ans;
		}else {
			String txt2=String.valueOf(Ans);
			return transform(txt2);
		}
	}
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int N=scan.nextInt();
		int ANS=1;
		for(int i=0;i<N;i++) {
			String Kstr=scan.next();
			int K=transform(Kstr);
			ANS*=K;
			String ANSstr=String.valueOf(ANS);
			ANS=transform(ANSstr);
		}
		
		System.out.println(ANS);
	}
}