Q, Y = map(int, input().split())
s = list(map(str, input().split()))

def solve(x):
    lst = []
    for i in range(Q):
        if s[i] in ['+', 'min', 'max']:
            val1 = lst[-1]
            val2 = lst[-2]
            lst.pop()
            lst.pop()
            if s[i] == '+':
                lst.append(val1 + val2)
            elif s[i] == 'min':
                lst.append(min(val1, val2))
            else:
                lst.append(max(val1, val2))
        else:
            if s[i] == 'X':
                lst.append(x)
            else:
                lst.append(int(s[i]))
    return lst[0]

ng = -1
ok = 10 ** 14 + 1

while ok - ng > 1:
    mid = (ok + ng) // 2
    solved = solve(mid)
    if solved < Y:
        ng = mid
    else:
        ok = mid

if solve(ok) != Y:
    print(-1)
else:
    print(ok)