if __name__ == '__main__':
    a, b = map(int, input().split())
    print(max(0, a - b * 2)) if __name__ == '__main__':
    a, b = map(int, input().split())
    print(max(0, a - b * 2)) __name__ == '__main__' __name__ '__main__' a, b = map(int, input().split()) a map(int, input().split()) map int input().split() ().split () input split b print(max(0, a - b * 2)) print max(0, a - b * 2) max 0 a - b * 2 a b * 2 b 2 b = map(int, input().split()) map(int, input().split()) b a, b = map(int, input().split()) map(int, input().split()) a
if __name__ == '__main__':
    a, b = map(int, input().split())
    print(max(0, a - b * 2))