#include<bits/stdc++.h>

#define ll long long
#define pi pair<int,int>
#define vi vector<int>
#define cpy(x,y,s) memcpy(x,y,sizeof(x[0])*(s))
#define mset(x,v,s) memset(x,v,sizeof(x[0])*(s))
#define all(x) begin(x),end(x)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ary array

#define N 500005

using namespace std;
int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0' || ch>'9')f=(ch=='-'?-1:f),ch=getchar();
    while(ch>='0' && ch<='9')x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
    return x*f;
}
void write(int x){
    if(x<0)x=-x,putchar('-');
    if(x/10)write(x/10);
    putchar(x%10+'0');
}

int a[N],b[N];

void add(int x,int val){
    if(x==0)return;
    int t=(x&(-x));b[__lg(t)]+=val;
}

void solve(){
    int n=read(),k=read(),sum=0,res=0;
    for(int i=0;i<=35;i++)b[i]=0;
    for(int i=1;i<=n;i++){
        a[i]=read();add(a[i],1);
        sum^=a[i];
    }
    if(k==0){write(sum);putchar('\n');return;}
    //cerr<<sum<<endl;
    for(int i=1;i<=n;i++){
        add(a[i],-1);add(a[i]+1,1);
        sum^=a[i];sum^=(a[i]+1);
        int nowres=2e9;
        for(int j=30;j>=0;j--){
            if(b[j]){
                nowres=min(nowres,sum^((1<<(j+1))-1));
            }
        }
        //cerr<<nowres<<' '<<i<<' '<<sum<<endl;
        res=max(res,nowres);
        sum^=(a[i]+1);sum^=a[i];
        add(a[i]+1,-1);add(a[i],1);
    }
    write(res);putchar('\n');
}

int main(){
    #ifdef EAST_CLOUD
    freopen("a.in","r",stdin);
    freopen("a.out","w",stdout);
    #endif

    int T=read();while(T--)solve();

    return 0;
}