from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math

N = int(input())
A = list(map(int,input().split()))
mod = 10**9 + 7



tmp = 1
X = [0,1,4,729]
if 0 in A:
    print(-1)
    exit()
for a in A:
    if a>=4:
        print(mod)
        exit()
    else:
        tmp *= X[a]
        if tmp > mod:
            print(mod)
            exit()
print(mod%tmp)