def linearSeach(data,key):
	for i in range(len(data)):
		if data[i] == key:
			return i
	return -1

def makeList(lenData):
	data = []
	for x in range(lenData):
		lol = int(input())
		data.append(lol)
	return(data)

def doIt():
	lenData,key = input().split()
	lenData = int(lenData)
	key = int(key)
	data = []
	if(lenData<0):
		return("Can't do that")
	else:
		data = makeList(lenData)
		return(linearSeach(data,key))

print(doIt())