import sys
from collections import deque, Counter
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())

n = ii()

a = li()
ans = 1
p = [0, 1, 4, 729]
for i in range(n):
    if a[i] > 4:
        print(10 ** 9 + 7)
        exit()
    else:
        ans *= p[a[i]]
        if ans > 10 ** 9 + 7:
            print(10 ** 9 + 7)

if ans == 0:
    print(-1)
else:
    print((10 ** 9 + 7) % ans)