a, b = list(map(int, input().split()))
print(max(a - b - b, 0)) a, b = list(map(int, input().split())) a list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split b print(max(a - b - b, 0)) print max(a - b - b, 0) max a - b - b a - b a b b 0 b = list(map(int, input().split())) list(map(int, input().split())) b a, b = list(map(int, input().split())) list(map(int, input().split())) a
a, b = list(map(int, input().split()))
print(max(a - b - b, 0))