from collections import deque
from operator import __add__

def calc(X):
	A=deque()
	for op in S:
		if op=="X":
			A.append(X)
		elif op=="+":
			A.append(A.pop()+A.pop())
		elif op=="min":
			A.append(min(A.pop(),A.pop()))
		elif op=="max":
			A.append(max(A.pop(),A.pop()))
		else:
			A.append(int(op))
	return A[0]
	
Q,Y=map(int,input().split())
S=input().split()
ok=1<<60
ng=-1
while ok-ng>1:
	mid=(ok+ng)//2
	if calc(mid)>=Y:
		ok=mid
	else:
		ng=mid
print(ok if calc(ok)==Y else -1)