import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int ans = 1;
        for (int i = 0; i < n; i++) {
            ans *= getNum(sc.nextLong());
            ans = getNum(ans);
        }
        System.out.println(ans);
    }
    
    static int getNum(long x) {
        if (x < 10) {
            return (int)x;
        }
        int sum = 0;
        while (x > 0) {
            sum += (int)(x % 10);
            x /= 10;
        }
        return getNum(sum);
    }
}