A,B = (int(x) for x in input().split())
print(max(0,A-2*B)) int(x) for x in input().split() for x in input().split() x input().split() ().split () input split for x in input().split() int(x) int x A,B = (int(x) for x in input().split()) A (int(x) for x 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(x) for x in input().split()) (int(x) for x in input().split()) B A,B = (int(x) for x in input().split()) (int(x) for x in input().split()) A
A,B = (int(x) for x in input().split())
print(max(0,A-2*B))