a, b = [int(i) for i in input("").split(" ")]
if a < 2*b:
  print(0)
else:
  print(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 if a < 2*b:
  print(0)
else:
  print(a - 2*b) a < 2*b a 2*b 2 b print(0) print 0 print(a - 2*b) print 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(" ")]
if a < 2*b:
  print(0)
else:
  print(a - 2*b)