N = int(input())
P = [int(p) for p in input().split()]

def f(n):
    n = str(n)
    res = 0
    for i in range(len(n)):
        res += int(n[i])
    return res

ans = 1
for i in range(N):
    ans *= P[i]
    while len(str(ans)) > 1:
        ans = f(ans)

print(ans)