#yuki1237
mod=1000000007
n=int(input())
a=list(map(int, input().split()))

if min(a)==0:
 print(-1)
 exit()
if max(a) >= 4:
 print(mod)
 exit()
res = 1
p=[1,1,4,729]
for i in a:
 res*=p[i]
 if res>mod:
  print(mod)
  exit()
print(mod%res)