Adjacent Xor 

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#include<bits/stdc++.h>

#define int long long

using namespace std;

int n,x,a[200001],dp[200001][2];

void nas() {

  cin >> n >> x;

  for(int i=1;i<=n;++i)

    cin >> a[i];

  for(int i=2;i<=n;++i) {

    dp[i][0]=max(dp[i-1][0]+(a[i-1]^a[i]),dp[i-1][1]+((a[i-1]+x)^a[i]));

    dp[i][1]=max(dp[i-1][0]+(a[i-1]^(a[i]+x)),dp[i-1][1]+((a[i-1]+x)^(a[i]+x)));

  }

  cout << max(dp[n][0],dp[n][1]) << endl;

}

signed main() {

  int T;

  cin >> T;

  while(T--) nas();

}