def main():
    A, B = (int(i) for i in input().split())
    print(max(A - 2*B, 0))


if __name__ == '__main__':
    main() def main():
    A, B = (int(i) for i in input().split())
    print(max(A - 2*B, 0)) main int(i) for i in input().split() for i in input().split() i input().split() ().split () input split for i in input().split() int(i) int i A, B = (int(i) for i in input().split()) A (int(i) for i in input().split()) B print(max(A - 2*B, 0)) print max(A - 2*B, 0) max A - 2*B A 2*B 2 B 0 if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    A, B = (int(i) for i in input().split())
    print(max(A - 2*B, 0)) def main():
    A, B = (int(i) for i in input().split())
    print(max(A - 2*B, 0)) main
def main():
    A, B = (int(i) for i in input().split())
    print(max(A - 2*B, 0))


if __name__ == '__main__':
    main()
