input_line = input()
inputs = input_line.split(' ')
inputs = [int(input) for input in inputs]

A = inputs[0]
B = inputs[1]

dual_B = 2 * B

res = 0
if A > dual_B:
    res = A - dual_B
else:
    res = 0

print(res) input_line = input() input_line input() input inputs = input_line.split(' ') inputs input_line.split(' ') input_line.split input_line split ' ' int(input) for input in inputs for input in inputs input inputs for input in inputs int(input) int input inputs = [int(input) for input in inputs] inputs [int(input) for input in inputs] A = inputs[0] A inputs[0] inputs 0 B = inputs[1] B inputs[1] inputs 1 dual_B = 2 * B dual_B 2 * B 2 B res = 0 res 0 if A > dual_B:
    res = A - dual_B
else:
    res = 0 A > dual_B A dual_B res = A - dual_B res A - dual_B A dual_B res = 0 res 0 print(res) print res input_line = input() input() input_line A = inputs[0] inputs[0] A dual_B = 2 * B 2 * B dual_B res = 0 0 res inputs = input_line.split(' ') input_line.split(' ') inputs res = 0 0 res res = A - dual_B A - dual_B res inputs = [int(input) for input in inputs] [int(input) for input in inputs] inputs B = inputs[1] inputs[1] B
input_line = input()
inputs = input_line.split(' ')
inputs = [int(input) for input in inputs]

A = inputs[0]
B = inputs[1]

dual_B = 2 * B

res = 0
if A > dual_B:
    res = A - dual_B
else:
    res = 0

print(res)
