Claris and XOR

Claris loves bitwise operations very much, especially XOR, because it has many beautiful features. He gets four positive integers $a,b,c,d$ that satisfies $a\leq b$ and $c\leq d$. He wants to choose two integers $x,y$ that satisfies $a\leq x\leq b$ and $c\leq y\leq d$, and maximize the value of $x~XOR~y$. But he doesn't know how to do it, so please tell him the maximum value of $x~XOR~y$.

The first line contains an integer $T\left(1\leq T\leq10,000\right)$——The number of the test cases.
For each test case, the only line contains four integers $a,b,c,d\left(1\leq a,b,c,d\leq10^{18}\right)$. Between each two adjacent integers there is a white space separated.

For each test case, the only line contains a integer that is the maximum value of $x~XOR~y$.

2
1 2 3 4
5 7 13 15

6
11

In the first test case, when and only when $x=2,y=4$, the value of $x~XOR~y$ is the maximum.
In the second test case, when and only when $x=5,y=14$ or $x=6,y=13$, the value of $x~XOR~y$ is the maximum.

BestCoder Round #79 (div.2)