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