from collections import deque
Q,Y=map(int,input().split())
S=list(map(str,input().split()))

def solve(n):
    # xをnとしたときの答え
    dq=deque()
    for i in range(Q):
        if S[i] == "X":
            dq.append(n)
        elif S[i] == "+":
            p1=dq.pop()
            p2=dq.pop()
            dq.append(p1+p2)
        elif S[i] == "min":
            p1=dq.pop()
            p2=dq.pop()
            dq.append(min(p1,p2))
        elif S[i] == "max":
            p1=dq.pop()
            p2=dq.pop()
            dq.append(max(p1,p2))
        else:
            dq.append(int(S[i]))
    return dq[0]

left, right= -1, 10**15
while right - left > 1:
    mid=(right+left)//2
    if solve(mid)>=Y:
        right=mid
    else:
        left=mid
if solve(right)!=Y:
    print(-1)
    exit(0)
print(right)