CF627A.XOR Equation

普及/提高-

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题目描述

Two positive integers $a$ and $b$ have a sum of $s$ and a bitwise XOR of $x$ . How many possible values are there for the ordered pair $(a,b)$ ?

输入格式

The first line of the input contains two integers $s$ and $x$ ( $2<=s<=10^{12}$ , $0<=x<=10^{12}$ ), the sum and bitwise xor of the pair of positive integers, respectively.

输出格式

Print a single integer, the number of solutions to the given conditions. If no solutions exist, print $0$ .

输入输出样例

输入#1
```
9 5
```
输出#1
```
4
```
输入#2
```
3 3
```
输出#2
```
2
```
输入#3
```
5 2
```
输出#3
```
0
```

说明/提示

In the first sample, we have the following solutions: $(2,7)$ , $(3,6)$ , $(6,3)$ , $(7,2)$ .

In the second sample, the only solutions are $(1,2)$ and $(2,1)$ .

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