a sneezing baby panda
Alex is taking care of a baby panda who seems to be
unusually sniffly. Every day, the baby panda may sneeze out
zero or one slime(s) into its enclosure; every night, all
slimes present in the enclosure split, so that the number of
slimes doubles overnight. Alex places the baby panda into a
clean enclosure with $0$
slimes at the beginning of day $1$ and observes that at the end of
night $n$, there are
$m$ slimes in the baby
panda’s enclosure. She is worried about the baby panda and
wants to know the number of times the baby panda sneezed out a
slime over these $n$
days.
Input
The only line of input contains the spaceseparated integers
$n, m$ ($1 \leq n \leq 10^{18}$, $0 \leq m \leq 10^{18}$, $m$ is even), where $n$ is the number of days and
$m$ is the number of
slimes present after night $n$.
Output
On a single line, output the number of times that the baby
panda sneezed out a slime.
Sample Input 1 
Sample Output 1 
10 10

2

Sample Input 2 
Sample Output 2 
10 128

1

Sample Input 3 
Sample Output 3 
13 500

6

Sample Input 4 
Sample Output 4 
1000000000000000000 576460752303423488

1
