func main()
	var n: int :: cui@inputInt()
	var a: []int :: #[n]int
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	if(a.min() = 0)
		do cui@print("-1\n")
		ret
	end if
	
	const c: int :: 1000000007
	if(a.max() > 3)
		do cui@print("\{c}\n")
		ret
	end if
	
	var val: []int :: [0, 1, 2 ^ 2, 3 ^ 6]
	var ans: int :: 1
	for i(0, n - 1)
		do ans :* val[a[i]]
		if(ans > c)
			break i
		end if
	end for
	do cui@print("\{c % ans}\n")
end func