mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    N, K = map(int, input().split())

    M = 1 + K
    m = N - K + 1
    if m > M:
        print(K+1)
    else:
        if N % 2 == 0:
            print(N // 2)
        else:
            if K % 2 == 0:
                print(min((N+1) // 2, (K//2) + 1) + min(N//2, K//2))
            else:
                print(min(N // 2, ((K+1) // 2)) + min((N+1) // 2, (K-1) // 2 + 1))


if __name__ == '__main__':
    main()