Q, Y = map(int, input().split())
S = input().split()

assert 1 <= Q <= 2 * 10**5
assert 0 <= Y <= 10**14
assert len(S) == Q

def rev_poland(x):
    A = []
    for s in S:
        if s in ('+', 'min', 'max'):
            a = A.pop()
            b = A.pop()
            
            if s == '+':
                A.append(a + b)
            if s == 'min':
                A.append(min(a, b))
            if s == 'max':
                A.append(max(a, b))
        
        else:
            if s == 'X':
                A.append(x)
            else:
                assert 0 <= int(s) <= 10**9
                A.append(int(s))
    
    return A[0]

ok, ng = 10**14, -1

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

if rev_poland(ok) == Y:
    print(ok)
else:
    print(-1)