Q, Y = map(int, input().split())
s = list(input().split())
def calc(x):
	A = []
	for i in s:
		if i == 'X':
			A.append(x)
		elif i == '+':
			A.append(A.pop() + A.pop())
		elif i == 'min':
			A.append(min(A.pop(), A.pop()))
		elif i == 'max':
			A.append(max(A.pop(), A.pop()))
		else:
			A.append(int(i))
	return A[0]
if calc(0) <= calc(10 ** 18):
	le = 0
	ri = 10 ** 18
	while le + 1 < ri:
		mi = (le + ri) // 2
		if calc(mi) >= Y:
			ri = mi
		else:
			le = mi
	if calc(le) == Y:
		print(le)
	elif calc(ri) == Y:
		print(ri)
	else:
		print(-1)
else:
	le = 0
	ri = 10 ** 18
	while le + 1 < ri:
		mi = (le + ri) // 2
		if calc(mi) <= Y:
			ri = mi
		else:
			le = mi
	if calc(le) == Y:
		print(le)
	elif calc(ri) == Y:
		print(ri)
	else:
		print(-1)