Problem:
 Score : 100 points    Problem Statement The window of Takahashi's room has a width of A . There are two curtains hung over the window, each of which has a horizontal length of B . (Vertically, the curtains are long enough to cover the whole window.)  We will close the window so as to minimize the total horizontal length of the uncovered part of the window.
Find the total horizontal length of the uncovered parts of the window then.      Constraints  1 \leq A \leq 100  1 \leq B \leq 100  A and B are integers.         Input Input is given from Standard Input in the following format:  A  B       Output Print the total horizontal length of the uncovered parts of the window.        Sample Input 1 12 4      Sample Output 1 4  We have a window with a horizontal length of 12 , and two curtains, each of length 4 , that cover both ends of the window, for example. The uncovered part has a horizontal length of 4 .       Sample Input 2 20 15      Sample Output 2 0  If the window is completely covered, print 0 .       Sample Input 3 20 30      Sample Output 3 0  Each curtain may be longer than the window.

Solution (Python):
A, B = map(int, input().split())
if A > 2*B:
    print(A - 2*B)
else:
    print(0)

Solution (Python):
a,b = map(int, input().split())
ans = a - 2*b
if ans > 0:
    print(ans)
else:
    print(0)

Solution (Python):
A,B = [int(x) for x in input().split()]

count = A - 2 * B

if count <= 0:
    print(0)
else:
    print(count)

Solution (Python):
a , b = map(int,input().split())
c = a - 2 * b

if c >= 0:
    print(c)
else:
    print(0)

Solution (Python):
import sys
def input(): return sys.stdin.readline().strip()
a,b=map(int,input().split())
if b*2>=a:
    print(0)
else:
    print(a-b*2)

Solution (Python):
if __name__ == '__main__':
    A, B = map(int, input().split())
    if A <= 2 * B:
        print(0)
    else:
        print(A - 2 * B)

Solution (Python):
a,b = [int(_) for _ in input().split()]
if a <= 2*b:
    ans = 0
else:
    ans = a - 2*b
print(ans)

Solution (Python):
A,B = list(map(int,input().split()))
ans = A - 2*B
if ans < 0:
  ans = 0
print(ans)

Solution (Python):
A,B = map(int,input().split())
remain = A-2*B
if remain <=0:
  print(0)
else:
  print(remain)

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

Solution (Python):
A,B = map(int,input().split())
print(max(0,A-2*B))

Solution (Python):
a,b = map(int,input().split())
if(a<=2*b):
    print(0)
else:
    print(a-2*b)

Solution (Python):
a, b = [int(x) for x in input().split()]

ret = max(0, a - 2 * b)

print(ret)

Solution (Python):
import sys
from fractions import gcd
from functools import reduce
from itertools import combinations
from random import random

import numpy as np

sys.setrecursionlimit(200000)


class Solver:
    def __init__(self):
        pass

    def input(self):
        """
            faster input function than builtin stdin.
        """
        return sys.stdin.readline()[:-1]

    def ii(self, t: type = int):
        """
            input single value.
        """
        return t(self.input())

    def il(self, t: type = int):
        """
            input single line.
        """
        return list(map(t, self.input().split()))

    def imi(self, N: int, t: type = int):
        return [self.ii(t) for _ in range(N)]

    def iml(self, N: int, t: type = int):
        return [self.il(t) for _ in range(N)]

    def solve(self):
        a, b = self.il()
        return a - 2 * b if a > 2 * b else 0


if __name__ == "__main__":
    solver = Solver()
    print(solver.solve())

Solution (Python):
A, B = map(int, input().split())
print("{}".format(A - 2*B if A - 2*B > 0 else 0))

Solution (Python):
a, b = map(int, input().split())

n = a - b * 2

if (n < 0):
    n = 0

print(n)

Solution (Python):
a, b = list(map(int, raw_input().split(" ")))

print(max(0, a-2*b))

Solution (Python):

a,b=map(int,input().split()) 

if 2*b>=a:
	print(0)
else:
	print(a-2*b)

Solution (Python):
a,b = list(map(int,input().split()))
print(max(0,a-2*b))

Solution (Python):
A, B = map(int, input().split())

ans = A - 2 * B

if ans <= 0:
  ans = 0
  
print(ans)

Solution (Python):
N,K = map(int, input().split())
print(max(0, N - 2*K))

Solution (Python):
A,B = [int(n) for n in input().split()]
print(A-B*2 if A>B*2 else 0)

Solution (Python):
A, B = map(int, input().split())

print(max(0, A-2*B))

Solution (Python):
a, b = map(int, input().split())
print(max(a-2*b,0))

Solution (Python):
A, B = tuple([int(x) for x in input().split(' ')])

print(max(A-2*B, 0))

Solution (Python):
a, b = map(int, input().split())

if a < 2 * b:
  print(0)
else:
  print(a-(2*b))

Solution (Python):



def ri():
    return int(input())

def rl():
    return list(input().split())

def rli():
    return list(map(int, input().split()))

def main():
    a, b = rli()
    print(max(0, a-2*b))


if __name__ == '__main__':
    main()

Solution (Python):
A, B = map(int, input().split())
print(max(0, A-B*2))

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

Solution (Python):
A, B=map(int, input().split())

if A>=2*B:
  print(A-2*B)
else:
  print(0)

Solution (Python):
A, B = map(int, input().strip().split())

ret = A - 2 * B

ans = ret if ret > 0 else 0
print(ans)

Solution (Python):
A, B = map(int, input().split())
if A>2*B:
    print(A-2*B)
else:
    print(0)

Solution (Python):
A,B = map(int,input().split())
print(max(A-2*B,0))

Solution (Python):
a,b = map(int, input().split())

if a - b*2 < 0:
  print(0)
  
else:
  print(a - b*2)

Solution (Python):
A,B = map(int, input().split())

if A <= B*2:
    print(0)
else:
    print(A-B*2)

Solution (Python):
A, B = map(int, input().split())

print(max(0, A-(2*B)))

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

Solution (Python):

A,B = map(int,input().split())

C = A - B * 2
if C >= 0:
    print(C)
else:
    print(0)

Solution (Python):
a,b=map(int,input().split())
c=a-b*2
if c<0:
  print("0")
else:
  print(c)

Solution (Python):

import sys

def solve():
  a,b = (int(i) for i in input().split())
  print(max(0,a-2*b))
solve()

Solution (Python):
A, B = [int(v) for v in input().split()]

print(max(0, A - 2 * B))

Solution (Python):
a, b = map(int, input().split())
if a <= 2 * b:
    print(0)
else:
    print(a - 2 * b)

Solution (Python):
n,k = map(int,input().split())
if(n > 2*k):
    print(n-2*k)
else:
    print(0)

Solution (Python):
a,b=map(int,raw_input().split())
c=b+b
print max(a-c,0)

Solution (Python):
a,b=map(int,input().split())

print(max(0,a-2*b))

Solution (Python):
a,b=map(int,input().split())

if a > b*2:
    print(a-b*2)
else:
    print(0)

Solution (Python):
a, b = map(int, input().split(" "))
if a < b*2:
  print(0)
else:
  print(a-2*b)

Solution (Python):
a,b = map(int,input().split())
c = a-2*b

if c>=0:
    print(c)
else:
    print("0")

Solution (Python):
a,s=map(int,input().split())
print(max(a-2*s,0))

Solution (Python):
a,b=map(int,input().split())
def main(a,b):
    ans=a-b*2
    if ans>0:
        print(ans)
    else:
        print(0)
main(a,b)

Solution (Python):
n,k = map(int,input().split())

if n-2*k >0:
  print(n-2*k)
else:
  print(0)

Solution (Python):
import sys
import math
from copy import deepcopy
from collections import deque, defaultdict
from operator import mul
from functools import reduce
sys.setrecursionlimit(20000000)




def main():
    A, B = map(int, input().split())

    print(A - (B * 2) if A >= B * 2 else 0)


if __name__ == '__main__':
    main()

Solution (Python):
A,B=map(int, input().split())
print(max(0, A-B*2))

Solution (Python):
A,B = map(int,input().split())
ans = max(A-2*B, 0)
print(ans)

Solution (Python):
import sys
input = sys.stdin.readline


a,b = map(int,input().split())
ans = a - b * 2
if ans<0 : ans = 0

print( ans )

Solution (Python):
import sys
input = sys.stdin.readline

a, b = map(int, input().split())

t = a  - b * 2

if t < 0:
  t = 0
  
print(t)

Solution (Python):
A,B=map(int,input().split())
if A<=B*2:
	print("0")
else:
	print(A-B*2)

Solution (Python):
a,b=map(int,input().split())
print(max(a-b*2,0))

Solution (Python):

import sys


def readline():
    return sys.stdin.readline().rstrip()


def read(f=int):
    return f(readline())


def reads(f=int):
    return list(map(f, readline().split()))


def read_n(n: int, f=int):
    return [read(f) for _ in range(n)]


def reads_n(n: int, f=int):
    return [reads(f) for _ in range(n)]

A, B = reads()

print(max([A - B * 2, 0]))

Solution (Python):
A, B = map(int, input().split())

if A <= 2 * B:
    print(0)
else:
    print(A - 2 * B)

Solution (Python):

from __future__ import division, print_function
from collections import defaultdict, Counter, deque
from future_builtins import ascii, filter, hex, map, oct, zip
from random import randint
from itertools import imap as map, izip as zip, permutations, combinations, combinations_with_replacement
from __builtin__ import xrange as range
from math import ceil
from _continuation import continulet
from cStringIO import StringIO
from io import IOBase
import __pypy__
from bisect import bisect, insort, bisect_left, bisect_right
import sys
import os
import re
sys.setrecursionlimit(9999)
inf = float('inf')
mod = int(1e9) + 7
mod_ = 998244353
N = 5001
 
'''
Check for special cases (n=1)
One wrong submission = 10 mins penalty!
do smth instead of nothing and stay organized
'''


def main():
	n, m = map(int, input().split())
	print(max(0, n-2*m))


BUFSIZE = 8192
class FastI(IOBase):
	def __init__(self, file):
		self._fd = file.fileno()
		self._buffer = StringIO()
		self.newlines = 0
 
	def read(self):
		while True:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			if not b:
				break
			ptr = self.buffer.tell()
			self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
		self.newlines = 0
		return self.buffer.read()
 
	def readline(self):
		while self.newlines == 0:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			self.newlines = b.count("\n") + (not b)
			ptr = self._buffer.tell()
			self._buffer.seek(0, 2), self._buffer.write(
				b), self._buffer.seek(ptr)
		self.newlines -= 1
		return self._buffer.readline()
class FastO(IOBase):
	def __init__(self, file):
		self._fd = file.fileno()
		self._buffer = __pypy__.builders.StringBuilder()
		self.write = lambda s: self._buffer.append(s)
 
	def flush(self):
		os.write(self._fd, self._buffer.build())
		self._buffer = __pypy__.builders.StringBuilder()
def print(*args, **kwargs):
	sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
	at_start = True
	for x in args:
		if not at_start:
			file.write(sep)
		file.write(str(x))
		at_start = False
	file.write(kwargs.pop("end", "\n"))
	if kwargs.pop("flush", False):
		file.flush()
def gcd(x, y):
	while y:
		x, y = y, x % y
	return x
sys.stdin, sys.stdout = FastI(sys.stdin), FastO(sys.stdout)
def input(): return sys.stdin.readline().rstrip("\r\n")
if __name__ == "__main__":
	def bootstrap(cont):
		call, arg = cont.switch()
		while True:
			call, arg = cont.switch(to=continulet(
				lambda _, f, args: f(*args), call, arg))
	cont = continulet(bootstrap)
	cont.switch()
	main()

Solution (Python):
a,b=map(int,input().split());print(max(a-2*b,0))

Solution (Python):

A, B = map(int, input().split())


print(max(0, A-2*B))

Solution (Python):
a, b = map(int, input().split())
if b*2 <=  a:
	print(a-b*2)
else:
	print(0)

Solution (Python):
a,b=map(int,input().split())
if a<(2*b):
  print(0)
else:
  print(a-(2*b))

Solution (Python):
a = input()
a,b = a.split()
a = int(a)
b = int(b)
if a <= b*2:
    print(0)
else:
    print(a-b*2)

Solution (Python):
if __name__ == '__main__':
    A, B = map(int, input().split())
    if A <= 2 * B:
        print(0)
    else:
        print(A - 2 * B)

Solution (Python):
A, B = map(int, input().split())
print(A-B*2 if A-B*2 > 0 else 0)

Solution (Python):
A,B = map(int,input().split())

BB= B*2

if BB > A :
    print(0)
else:
    print(A-BB)

Solution (Python):






import math
import statistics
import numpy as np

a,b = map(int, input().split())
if(a <= 2 * b):
  print('0')
else:
  print(a - b * 2)

Solution (Python):
A, B = list(map(int, input().split()))

print(max(0, A-B*2))

Solution (Python):
A, B = [int(i) for i in input().split()]
print(max(0, A-2*B))

Solution (Python):
a, b  = map(int, input().split())
print(max(0, a-2*b))

Solution (Python):
A, B = map(int, input().split())
if A-2*B < 0:
    print(0)
else:
    print(A-2*B)

Solution (Python):
A, B = map(int, input().split())
print(max(0, A - 2 * B))

Solution (Python):
a,b = map(int, input().split())

c = a - 2*b
if c <= 0:
    c = 0
print(c)

Solution (Python):
A, B = map(int, input().split())

if A > B * 2:
    print(A-2*B)
else:
    print(0)

Solution (Python):
A, B = map(int, input().split())

ans = A-B*2
if ans<0:
    ans = 0

print(ans)

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

Solution (Python):
a, b = map(int, input().split())
print(max(0, a-b*2))

Solution (Python):
if __name__ == "__main__":
    A, B = map(int, input().split())

    ans = A - B * 2

    if ans < 0:
        print('0')
    else:
        print(ans)

Solution (Python):
A, B = [int(i) for i in input().split()]

if A < B*2:
    print(0)
else:
    print(A - B*2)

Solution (Python):






def main():

    a,b=map(int,input().split())
    c=a-b*2
    if c<0:
        c=0
    print(c)






if __name__ == "__main__":
    main()

Solution (Python):
def read():
    A, B = list(map(int, input().strip().split()))
    return A, B

def solve(A, B):
    return max(0, A - B * 2)

if __name__ == '__main__':
    inputs = read()
    print("%d" % solve(*inputs))

Solution (Python):
a,b=map(int, input().split())

c =a-2*b

if c<0:
  print(0)
else:
  print(c)

Solution (Python):
a, b = [int(i) for i in input().split()]
print(max(a-2*b, 0))

Solution (Python):
a,b = map(int,input().split())
 
if a <= b*2:
  print(0)
else:
  print(a-b*2)

Solution (Python):
A, B = map(int, input().split())
if A <= 2 * B:
    print(0)
else:
    print(A - 2 * B)

Solution (Python):
a, b = map(int,input().split())	

c = a - 2*b

if c>=0:
  print(c)
else:
  print(0)

Solution (Python):
A,B = map(int, input().split(' '))
print(max(A-2*B,0))

Solution (Python):
a, b = map(int, input().split())
if (a - 2*b) <= 0:
    print(0)
else:
    print(a - 2*b)

Solution (Python):
A,B = map(int,input().split())
ans = max(0,A-2*B)
print(ans)

Solution (Python):


import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

A, B = MAP()

print(max(A - B*2, 0))

Solution (Python):
A, B = map(int,input().split())
print(max(0, A - B * 2))

Solution (Python):
import sys
input = sys.stdin.readline

A, B = (int(i) for i in input().split())


if A-2*B > 0:
    print(A-2*B)
else:
    print(0)

Solution (Python):
a,b=map(int,input().split())
if a<=b*2:
    print(0)
else:
    print(a-b*2)

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

Solution (Python):
A, B = map(int, input().split())
ans = A-B*2
if ans > 0:
    print(ans)
else:
    print(0)

Solution (Python):
a, b = map(int, input().split())
print(max(a-2*b, 0))

Solution (Python):
a, b = map(int, input().split())

c = a - 2*b

if c < 0:
    c=0
    
print(c)

Solution (Python):


def main():
    A,B = map(int, input().split())
    print(max(0, A-2*B))


if __name__ == '__main__':
    main()

Solution (Python):
a, b = map(int, input().split())
if (a > b * 2):
    print(a-b*2)
else:
    print("0")

Solution (Python):
a, b = map(int, input().split())
print(max(0, a - b * 2))

Solution (Python):
a, b = map(int, input().split( ))
print(max(0,a-2*b))

Solution (Python):
a, b = map(int, input().split())

print(max(0, a-2*b))

Solution (Python):
A,B = map(int, input().split())

ret = A - B * 2
print(0 if ret < 0 else ret)

Solution (Python):
a,b = map(int,input().split())
if a <= b*2:
    print(0)
else:
    print(a-b*2)

Solution (Python):
A, B = map(int, input().split())

C = B*2

if A > C:
    print(A-C)
else:
    print(0)

Solution (Python):
A, B = map(int, raw_input().split())

res = A - 2*B
if res < 0:
    print 0
else:
    print res

Solution (Python):
(N, M) = tuple([int(s) for s in input().split()])
print(max(N - M * 2, 0))

Solution (Python):
a,b = map(int,input().split())
print(max(0,int(a-2*b)))

Solution (Python):
a,b = map(int,input().split())

ans = a - 2*b

if ans < 0 :
	print(0)
else:
	print(ans)

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

Solution (Python):
def solve():
  A, B = map(int, input().split())
  return max(0, A - 2 * B)

print(solve())

Solution (Python):
A,B=map(int,input().split())
if A-2*B>=0:
  print(A-2*B)
else:
  print(0)

Solution (Python):
a, b = map(int, input().split())
ans = a-2*b
if ans > 0:
    print(ans)
else:
    print(0)

Solution (Python):

a, b = list(map(int,input().split()))

result = max(a - b * 2, 0)

print(str(result))

Solution (Python):
a,b = map(int,input().split())
if a <= b*2:
  print(0)
else:
  print(a-b*2)

Solution (Python):
'''
import sys
input=sys.stdin.readline
n,m,c = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
from math import ceil
from collections import defaultdict ,Counter
'''
a,b = map(int,input().split())
print(max(0,a - b*2))

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

Solution (Python):

A, B = map(int,input().split())
print(max(A-2*B,0))

Solution (Python):
A, B = map(int,input().split())
S = A-B*2

if S<0:
  print(0)
else:
  print(S)

Solution (Python):
import sys
import re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy, copy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd


def input(): return sys.stdin.readline().strip()


def INT(): return int(input())


def MAP(): return map(int, input().split())


def LIST(): return list(map(int, input().split()))


sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7


def main():
    a, b = MAP()
    if a <= 2* b:
        print(0)
    else:
        print(a - 2 * b)

if __name__ == '__main__':
    main()

Solution (Python):
a, b = list(map(int, input().split()))
print(max(0, a - 2 * b))

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

Solution (Python):
a,b = map(int, input().split())
print(max(a-2*b,0))

Solution (Python):
A, B = map(int, input().split())
def curtain(a, b):
    return max(0, a-2*b)
out = curtain(A, B)
print(out)

Solution (Python):


a, b = map(int, input().split())

print(max(0, a - 2 * b))

Solution (Python):


A,B =map(int,input().split())
if (A-2*B)>=0:
    print(A-2*B)
else:
    print(0)

Solution (Python):
A, B = map(int, input().split())
c = A - 2*B
if c < 0:
    c = 0

print(c)

Solution (Python):
def f_a():
    a, b = map(int, input().split())
    o = a-2*b if a>=2*b else 0
    print(o)

if __name__ == "__main__":
    f_a()

Solution (Python):
A,B=map(int,input().split())
if A<=2*B:
  print(0)
else:
  print(A-2*B)

Solution (Python):
a,b= map(int,input().split())
r = a-b*2
if r <= 0:
    print(0)
else:
    print(r)

Solution (Python):
A,B=map(int,input().split())
if A>=2*B:
    print(A-2*B)
else:
    print(0)

Solution (Python):
A,B=list(map(int,input().split()))

print(max(A-2*B,0))

Solution (Python):
A, B = map(int, input().split())
print(max(A - 2 * B, 0))

Solution (Python):
n, m = map(int, input().split())

l = m*2

if n -l < 0:
    print(0)
else:
    print(n-l)

Solution (Python):
A, B = map(int, input().split())

if A <= 2 * B:
	print(0)
else:
	print(A - 2 * B)

Solution (Python):
A = list(map(int, input().split())) 
print(max(0,A[0]-2*A[1]))

Solution (Python):

x,y = map(int,input().split())










a=x-2*y
if(a<0):
    print(0)
else:
    print(a)

Solution (Python):
def main():

    A, B = map(int, input().split())
    if B*2 >= A: return 0
    else: return A - 2*B

if __name__ == '__main__':
    print(main())

Solution (Python):
a,b =map(int,input().split())
print(max(0,a-2*b))

Solution (Python):
a, b = map(int, input().split())

if (b*2 >= a):
    print(0)
else:
    print(a- b * 2)

Solution (Python):
import sys

sys.setrecursionlimit(4100000)


def inputs(num_of_input):
    ins = [input() for i in range(num_of_input)]
    return ins


def solve(inputs):
    [A, B] = string_to_int(inputs[0])

    C = A - 2 * B

    if C >= 0:
        return C
    else:
        return 0


def string_to_int(string):
    return list(map(lambda x: int(x), string.split()))


if __name__ == "__main__":
    ret = solve(inputs(1))
    print(ret)

Solution (Python):
A, B = map(int, input().split())
if A > B*2:
  print(A - B*2)
else:
  print(0)

Solution (Python):
a,b = list(map(int, input().split()))

c=a-2*b
if c<0:
    c=0
    
print(c)

Solution (Python):
a, b = map(int, input().split())
print(max(0, a - b * 2))

Solution (Python):
a,b = map(int,input().split())
print(max(a-2*b,0))

Solution (Python):
A, B = map(int, input().split())
print(max(A - 2 * B, 0))

Solution (Python):
A, B = list(map(int, input().split()))
print(max(0, A - B * 2))

Solution (Python):
A, B = map(int, input().split())

if 2 * B >= A:
    print(0)
else:
    print(int(A-2*B))

Solution (Python):
A, B = map(int, input().split(" "))
if A <= 2 * B:
    print(0)
else:
    print(A - 2 * B)

Solution (Python):
[a,b]=list(map(int,input().split()))
nagasa=int(a-2*b)
if nagasa<0:
	nagasa=0
print(nagasa)

Solution (Python):
a, b = map(int, input().split())
print(max(0, a - 2 * b))

Solution (Python):
A, B = map(int, input().split())
r = A - 2*B
print(r if r > 0 else 0)

Solution (Python):
a, b = map(int, input().split())
print(max(0, a - 2*b))

Solution (Python):



def rint():
    return int(input())


def rints():
    return list(map(int, input().split()))


a, b = rints()
print(max(0, a - 2 * b))

Solution (Python):
A, B = map(int, input().split())

if A <= B*2:
  print(0)
else:
  print(A-2*B)

Solution (Python):
from collections import Counter,defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue
sys.setrecursionlimit(10**8)
mod = 10**9+7
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))
def inpl_str(): return list(sys.stdin.readline().split())
def inpln(n): return list(int(sys.stdin.readline()) for i in range(n))

a,b = inpl()
print(max(0, a-b*2))

Solution (Python):
A, B = map(int, input().split())

if A - (B*2) > 0:
    print(A - (B*2))
else:
    print(0)

Solution (Python):
A,B = map(int,input().split())
if A>=2*B:
    print(A-2*B)
else:
    print(0)

Solution (Python):
import sys
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))
mod = 10**9 + 7
inf = float('inf')
A,B = LI()
ans = int(0)

ans = max(A-2*B,0)


print(ans)

Solution (Python):
A,B = map(int, input().split())

if A > B * 2:
    print(A-B*2)
else:
    print(0)

Solution (Python):
A, B=map(int,input().split())
print(A-2*B if A > B*2 else 0)

Solution (Python):
hoge = input().split()
a = int(hoge[0])
b = int(hoge[1])

ans = a - 2 * b

if ans < 0:
  print(0)
else:
  print(ans)

Solution (Python):
A,B = list(map(int,input().split()))

if A-2*B >= 0:
    print(A-2*B)
else:
    print(0)

Solution (Python):
import sys; readline = sys.stdin.readline
from collections import deque


A, B = map(int, readline().split())
print(max(0, A - 2 * B))

Solution (Python):
K,S = list(map(int,input().split()))

X = K - S*2

if X < 0:
  print(0)
else:
  print(X)

Solution (Python):
n,m = list(map(int,input().split()))
a = n-m*2
if a <0:
  a=0
print(a)

Solution (Python):

a,b = map(int, input().split())
print(max(0, a-2*b))

Solution (Python):
a, b= [int(x) for x in input().split()]
print(max(a - 2 * b, 0))

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

Solution (Python):
a=[]
for x in input().split(" "):
    a.append(int(x))

if a[0]<2*a[1]:
    print(0)
else:
    print(a[0]-2*a[1])

Solution (Python):
A, B = map(int, input().split())
ans = A - (2 * B)
if ans < 0:
  print(0)
else:
  print(ans)

Solution (Python):
a,b = map(int, input().split())

res = a - (b*2)
if res < 0:
  print(0)
else:
  print(res)

Solution (Python):
tmp = input().split()
A = int(tmp[0])
B = int(tmp[1])

ans = A - B * 2
if ans < 0:
    ans = 0
print(ans)

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

Solution (Python):
a, b = map(int, input().split())
print(max(0, (a-b*2)))

Solution (Python):
m,n=map(int,input().split())
if m>2*n:
  print(m-2*n)
else:
  print(0)

Solution (Python):
a, b = map(int, input().split())
res = a - 2*b
if res < 0:
    res = 0
print(res)

Solution (Python):
A,B=map(int,input().split())

if A>=2*B:
  print(A-2*B)
else:
  print(0)

Solution (Python):
A, B = map(int,input().split())
print(max(0,A-2*B))

Solution (Python):
a, b = list(map(int, input().split()))
c =a-2*b
if c < 0:
    print(0)
else:
    print(c)

Solution (Python):
A, B = map(int, input().split())
print(max(A-B*2, 0))

Solution (Python):
A, B = list(map(int, input().split()))

if 2 * B >= A:
    print(0)
else:
    print(A-B-B)

Solution (Python):
a, b = map(int, input().split())

print(max(0, a - 2 * b))

Solution (Python):


from collections import deque, defaultdict
import itertools as ite
import sys
import math
import decimal

sys.setrecursionlimit(1000000)

INF = 10 ** 18
MOD = 10 ** 9 + 7

A, B = map(int, raw_input().split())
print max(0, A - 2 * B)

Solution (Python):
a, b = tuple(map(int, input().split()))

if a  < 2*b:
    print(0)
else:
    print(a -2*b)

Solution (Python):
def main():
    A, B = map(int, input().split())

    if A < B*2:
        print('0')
    else:
        print(A-B*2) 


if __name__ == '__main__':
    main()

Solution (Python):
A, B = map(int, input().split())

print(max(A-2*B, 0))

Solution (Python):
a,b = map(int,input().split())
print(max(a-2*b,0))

Solution (Python):
a, b= map(int, input().split())
ans=a-b*2
if ans<0:
    ans=0
print(ans)

Solution (Python):
A,B=map(int,input().split())
if A>=2*B:
  print(A-2*B)
else:
  print(0)

Solution (Python):
a, b = list(map(int, input().split()))
if a >= b*2:
    print(a-b*2)
else:
    print(0)

Solution (Python):
A,B = map(int,input().split())
if A-(B*2) < 0:
    print(0)
else:
    print(A-(B*2))

Solution (Python):
a, b = map(int, input().split())
print(max(a - 2 * b, 0))

Solution (Python):
def main():
    a, b = map(int, input().split(' '))
    print(max(0, a - 2*b))


if __name__ == '__main__':
    main()

Solution (Python):
a, b = map(int, input().split())
ans = max(0, a - 2*b)
print(ans)

Solution (Python):


a, b = map(int, input().split())

if a >= b * 2:
    print(a - b*2)
else:
    print(0)

Solution (Python):

a, b = map(int, input().split())
print(max(a-b*2, 0))

Solution (Python):
def main():
    a,b = map(int,input().split())
    print(max((a-2*b),0))
if __name__ == "__main__":
    main()

Solution (Python):
a,b = map(int,raw_input().split())
print max(0, a-2*b)

Solution (Python):
A,B = map(int,input().split())

if A - 2 * B > 0:
    print(A - 2 * B)
else:
    print(0)

Solution (Python):
a,b = map(int,input().split())
if a <= b*2:
  print(0)
else:
  print(a-(b*2))

Solution (Python):
A, B = map(int, input().split())
print(max(A-2*B, 0))

Solution (Python):
from collections import deque,defaultdict,Counter
from itertools import accumulate
import bisect
from heapq import heappop,heappush
from fractions import gcd
from copy import deepcopy
import math
import queue


Mod = 1000000007
 
  
def sieve_of_eratosthenes(n):
    if not isinstance(n,int):
        raise TypeError("n is not int")
    if n<2:
        raise ValueError("n is not effective")
    prime = [1]*(n+1)
    for i in range(2,int(math.sqrt(n))+1):
        if prime[i] == 1:
            for j in range(2*i,n+1):
                if j%i == 0:
                    prime[j] = 0
    res = []
    for i in range(2,n+1):
        if prime[i] == 1:
            res.append(i)
    return res

def factorial(i):
    if i == 1:
        return 1
    else:
        return i*factorial(i-1)
 
class UnionFind:
    def __init__(self,n):
        self.parent = [i for i in range(n+1)]
        self.rank = [0 for i in range(n+1)]
    
    def findroot(self,x):
        if x == self.parent[x]:
            return x
        else:
            y = self.parent[x]
            y = self.findroot(self.parent[x])
            return y
    
    def union(self,x,y):
        px = self.findroot(x)
        py = self.findroot(y)
        if px < py:
            self.parent[py] = px
        else:
            self.parent[px] = py
 
    def same_group_or_no(self,x,y):
        return self.findroot(x) == self.findroot(y)




def main(): 
    A,B = map(int,input().split())
    print(max(0,A-2*B))
if __name__ == "__main__":
    main()

Solution (Python):
a,b = list(map(int,input().split()))
print(a-b*2 if a>b*2 else 0)

Solution (Python):
a, b = map(int, input().split())
ans = a - b * 2
if ans < 0:
    ans = 0
print(ans)

Solution (Python):
A, B = [int(item) for item in input().split()]
print(max(0, A-B-B))

Solution (Python):
a, b = map(int, input().split())


if a - 2 * b <= 0:
    print(0)
else:
    print(a-2*b)

Solution (Python):
a, b = map(int, input().split())

ans = a-b*2
if ans <= 0:
    print('0')
else:
    print(ans)

Solution (Python):


import sys

s2nn = lambda s: [int(c) for c in s.split(' ')]
ss2nn = lambda ss: [int(s) for s in list(ss)]
ss2nnn = lambda ss: [s2nn(s) for s in list(ss)]
i2s = lambda: sys.stdin.readline().rstrip()
i2n = lambda: int(i2s())
i2nn = lambda: s2nn(i2s())
ii2ss = lambda n: [i2s() for _ in range(n)]
ii2nn = lambda n: ss2nn(ii2ss(n))
ii2nnn = lambda n: ss2nnn(ii2ss(n))

def main():
    A, B = i2nn()
    print(A - 2 * B if A > (2 * B) else 0)
    return

main()

Solution (Python):
A, B = map(int, input().split())

ans = A - B*2
if ans < 0:
    print(0)
else:
    print(ans)

Solution (Python):
a,b = map(int, input().split())

if b * 2 >= a:
    print(0)
else:
    print(a - b * 2)

Solution (Python):
a,b  = map(int,input().split())

if a > 2*b:
    print(int(a-2*b))
else:
    print(0)

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

Solution (Python):
a,b=  list(map(int,input().split(" ")))
print(max(0,a-2 * b))

Solution (Python):
import sys
sys.setrecursionlimit(10**7)
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def II(): return int(sys.stdin.readline())
def SI(): return sys.stdin.readline().strip()
INF = 10 ** 18
MOD = 10 ** 9 + 7


debug = False

def dprint(*objects):
    if debug == True:
        print(*objects)

def solve():
    A, B = LI()

    print(max(0, A-2*B))

solve()

Solution (Python):
A, B = map(int, input().split())

x = A - B - B

if x > 0:
    print(x)
else:
    print(0)

Solution (Python):
A, B = map(int, input().split())

if A - 2*B <0:
  ans = 0
else:
  ans = A - 2*B
  
print(ans)