import java.util.*;
public class SSd {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.nextLine().trim());
        String ar[] = sc.nextLine().split(" ");
        long mul = 1;
        long nums[] = new long[n];
        for(int i=0;i<n;i++) {
            long cur = Long.parseLong(ar[i]);
            mul *= getSum(cur);
            mul = getSum(mul);
        }
        while(mul>10)
            mul =getSum(mul);
        System.out.println(mul);
    }
    static long getSum(long n){
        long sum = 0;
        while(n!=0){
            sum += n%10;
            n /= 10;
        }
        return sum;
    }
}