import sys
input = sys.stdin.readline

N=int(input())
A=list(map(int,input().split()))

X=[0]
Z=1
for i in range(1,4):
    Z*=i
    X.append(i**Z)
    

if 0 in A:
    print(-1)
else:
    ANS=1

    for a in A:
        if a>3 or ANS>10**9+7:
            print(10**9+7)
            break
        else:
            ANS*=X[a]
    else:
        print((10**9+7)%ANS)