# coding: utf-8
# Your code here!

def ketawa(x):
    while x > 9:
        y = 0
        while x > 0:
            y += (x % 10)
            x = x // 10
        x = y
    return x

N = int(input())
X = 1
P = input().split()
for i in P:
    X = ketawa(X * ketawa(int(i)))
print(X)