from collections import defaultdict
import sys
readline=sys.stdin.readline

N=int(readline())
A=list(map(int,readline().split()))
mod=10**9+7
if any(a>=4  for a in A):
    ans=mod
elif any(a==0 for a in A):
    ans=-1
else:
    x=1
    for a in A:
        if a==1:
            x*=1
        elif a==2:
            x*=2**2
        else:
            x*=3**6
        if x>=mod:
            ans=mod
            break
    else:
        ans=mod%x
print(ans)