# Generated by ChatGPT-4o

def evaluate_rpn(expression, x):
    stack = []
    for token in expression:
        if token == 'X':
            stack.append(x)
        elif token.isdigit():
            stack.append(int(token))
        else:
            b = stack.pop()
            a = stack.pop()
            if token == '+':
                stack.append(a + b)
            elif token == 'min':
                stack.append(min(a, b))
            elif token == 'max':
                stack.append(max(a, b))
    return stack[0]

def find_min_x(Q, Y, S):
    left, right = 0, 10**14
    result = -1
    
    while left <= right:
        mid = (left + right) // 2
        if evaluate_rpn(S, mid) == Y:
            result = mid
            right = mid - 1
        elif evaluate_rpn(S, mid) < Y:
            left = mid + 1
        else:
            right = mid - 1
            
    return result

if __name__ == "__main__":
    import sys
    input = sys.stdin.read
    data = input().split()
    
    Q = int(data[0])
    Y = int(data[1])
    S = data[2:]
    
    result = find_min_x(Q, Y, S)
    print(result)