import sys

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

A, B = lr()
answer = max(0, A - (B + B))
print(answer) import sys sys sr = lambda: sys.stdin.readline().rstrip() sr lambda: sys.stdin.readline().rstrip() sys.stdin.readline().rstrip() sys.stdin.readline().rstrip sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline rstrip ir = lambda: int(sr()) ir lambda: int(sr()) int(sr()) int sr() sr lr = lambda: list(map(int, sr().split())) lr lambda: list(map(int, sr().split())) list(map(int, sr().split())) list map(int, sr().split()) map int sr().split() ().split () sr split A, B = lr() A lr() lr B answer = max(0, A - (B + B)) answer max(0, A - (B + B)) max 0 A - (B + B) A B + B B B print(answer) print answer ir = lambda: int(sr()) lambda: int(sr()) ir A, B = lr() lr() A lr = lambda: list(map(int, sr().split())) lambda: list(map(int, sr().split())) lr B = lr() lr() B sr = lambda: sys.stdin.readline().rstrip() lambda: sys.stdin.readline().rstrip() sr answer = max(0, A - (B + B)) max(0, A - (B + B)) answer
import sys

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

A, B = lr()
answer = max(0, A - (B + B))
print(answer)
