import itertools

n, k = map(int,input().split())

num_list = list(range(1, n + 1))
split_list = []
res = 0

for i in range(1, n // 2 + 1):
    split_list.append([i, n - i])
    if i != n - i:
        split_list.append([n - i, i])

for i in range(len(split_list)):
    cur_list = list(itertools.combinations(num_list, split_list[i][0]))

    for j in range(len(cur_list)):
        one_list = cur_list[j]
        another_list = [e for e in num_list if e not in cur_list[j]]
        
        if one_list[0] == k and max(one_list) > min(another_list):
            res += 1
            
print(res)