a,b=(int(i) for i in input().split())
print(max(0,a-(2*b))) 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(0,a-(2*b))) print max(0,a-(2*b)) max 0 a-(2*b) a 2*b 2 b b=(int(i) for i in input().split()) (int(i) for i in input().split()) b a,b=(int(i) for i in input().split()) (int(i) for i in input().split()) a
a,b=(int(i) for i in input().split())
print(max(0,a-(2*b)))