import sequtils,strutils
var
    N, K, ans, n : int64
(N, K) = stdin.readline.split.map(parseBiggestInt)
for i in 1 .. (N * 2):
    for j in 0 .. min(i,300):
        var
            x = i - j
        if (i and x) == N and i > x:
            ans += 1

echo ans