func main()
	var n: int :: cui@inputInt()
	var ans: int :: 1
	for loop(1, n)
		var p: int :: cui@inputInt()
		if(p = 0)
			do ans :: -1
			break loop
		end if
		do ans :* p
		do ans :% 9
	end for
	switch(ans)
	case -1
		do ans :: 0
	case 0
		do ans :: 9
	end switch
	do cui@print("\{ans}\n")
end func