q, y = map(int, input().split())
s = input().split()

def calc(x):
    stack = []
    for i in range(q):
        if s[i] == '+':
            a = stack.pop()
            stack[-1] += a
        elif s[i] == 'min':
            a = stack.pop()
            stack[-1] = min(stack[-1], a)
        elif s[i] == 'max':
            a = stack.pop()
            stack[-1] = max(stack[-1], a)
        elif s[i] == 'X':
            stack.append(x)
        else:
            stack.append(int(s[i]))
    return stack[0]


l = -1
r = y+1

while l + 1 < r:
    mid = (l + r)//2
    if calc(mid) < y:
        l = mid
    else:
        r = mid
if calc(r) == y:
    print(r)
else:
    print(-1)