a, b = map(int, input().split())
res = a-2*b if (a-2*b >= 0) else 0
print(res)
1f8c1c5e4a5d47826db2b0b4bb684c736d01d05e
<mask token>

<mask token>
print(res)

a, b = map(int, input().split())
res = a - 2 * b if a - 2 * b >= 0 else 0
print(res)

a, b = map(int, input().split())
res = a-2*b if (a-2*b >= 0) else 0
print(res)