import java.util.*;

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