CF1013B.And

普及/提高-

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题目描述

There is an array with $n$ elements $a_{1},a_{2},...,a_{n}$ and the number $x$ .

In one operation you can select some $i$ ( $1<=i<=n$ ) and replace element $a_{i}$ with a_{i}&x , where & denotes the bitwise and operation.

You want the array to have at least two equal elements after applying some operations (possibly, none). In other words, there should be at least two distinct indices $i≠j$ such that $a_{i}=a_{j}$ . Determine whether it is possible to achieve and, if possible, the minimal number of operations to apply.

输入格式

The first line contains integers $n$ and $x$ ( $2<=n<=100000$ , $1<=x<=100000$ ), number of elements in the array and the number to and with.

The second line contains $n$ integers $a_{i}$ ( $1<=a_{i}<=100000$ ), the elements of the array.

输出格式

Print a single integer denoting the minimal number of operations to do, or -1, if it is impossible.

输入输出样例

输入#1
```
4 3
1 2 3 7
```
输出#1
```
1
```
输入#2
```
2 228
1 1
```
输出#2
```
0
```
输入#3
```
3 7
1 2 3
```
输出#3
```
-1
```

说明/提示

In the first example one can apply the operation to the last element of the array. That replaces 7 with 3, so we achieve the goal in one move.

In the second example the array already has two equal elements.

In the third example applying the operation won't change the array at all, so it is impossible to make some pair of elements equal.

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