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