a = list(map(int, input().split()))
b= a[0] - a[1] * 2
if b <= 0:
  print(0)
else:
  print(b) a = list(map(int, input().split())) a list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split b= a[0] - a[1] * 2 b a[0] - a[1] * 2 a[0] a 0 a[1] * 2 a[1] a 1 2 if b <= 0:
  print(0)
else:
  print(b) b <= 0 b 0 print(0) print 0 print(b) print b b= a[0] - a[1] * 2 a[0] - a[1] * 2 b a = list(map(int, input().split())) list(map(int, input().split())) a
a = list(map(int, input().split()))
b= a[0] - a[1] * 2
if b <= 0:
  print(0)
else:
  print(b)