#include <iostream>
#include <algorithm>
#include <assert.h>
#include <stack>
using namespace std;


int readPosIntLn(){
	int x=0;
	int cnt=0;
	int fi=-1;
	while(true){
		char g=getchar();
		if('0'<=g && g<='9'){
			x*=10;
			x+=g-'0';
			if(cnt==0){
				fi=g-'0';
			}
			cnt++;
			assert(!(cnt>10 || ( cnt==10 && fi>1) ));
		} else if(g=='\n'){
			return x;
		} else {
			assert(false);
		}
	}
}
 
long long readPosLongLn(){
	long long x=0;
	int cnt=0;
	int fi=-1;
	while(true){
		char g=getchar();
		if('0'<=g && g<='9'){
			x*=10;
			x+=g-'0';
			if(cnt==0){
				fi=g-'0';
			}
			cnt++;
			assert(!(cnt>20 || ( cnt==19 && fi>1) ));
		} else if(g=='\n'){
			return x;
		} else {
			assert(false);
		}
	}
}
 
int readPosIntSpace(){
	int x=0;
	int cnt=0;
	int fi=-1;
	while(true){
		char g=getchar();
		if('0'<=g && g<='9'){
			x*=10;
			x+=g-'0';
			if(cnt==0){
				fi=g-'0';
			}
			cnt++;
			assert(!(cnt>10 || ( cnt==10 && fi>1) ));
		} else if(g==' '){
			return x;
		} else {
			assert(false);
		}
	}
}
 
 
long long readPosLongSpace(){
	long long x=0;
	int cnt=0;
	int fi=-1;
	while(true){
		char g=getchar();
		if('0'<=g && g<='9'){
			x*=10;
			x+=g-'0';
			if(cnt==0){
				fi=g-'0';
			}
			cnt++;
			assert(!(cnt>20 || ( cnt==19 && fi>1) ));
		} else if(g==' '){
			return x;
		} else {
			assert(false);
		}
	}
}
 



struct Gauss{
	int arr[31];
	int len;
	Gauss(){
		len=0;
	}
	void add(int x){
		for(int i=0;i<len;i++){
			if( (arr[i]^x)< x)
				x=arr[i]^x;
		}
		if(x!=0){
			arr[len++]=x;
			int cur=len-1;
			for(int i=len-1;i>0;i--){
				if(arr[i]>arr[i-1]){
					cur=i-1;
					swap(arr[i],arr[i-1]);
				}
			}
		}
	}
	int getMax(){
		int ret=0;
		for(int i=0;i<len;i++){
			if((ret^arr[i]) > ret){
				ret= ret^arr[i];
			}
		}
		return ret;
	}
};


Gauss Merge(Gauss a,Gauss b){
	if(a.len > b.len){
		swap(a,b);
	}
	for(int i=0;i<a.len;i++){
		b.add(a.arr[i]);
	}
	return b;
}

int n;
int T;
long long k;
int c[100100];
int d[100100];
int main(){
	//freopen("08.txt","r",stdin);
	//freopen("08o.txt","w",stdout);
	cin.sync_with_stdio(false);
	T=readPosIntLn();
	assert(1<=T && T<=10000);
	//cin>>T;
	int sm=0;
	while(T--){
		//cin>>n>>k;
		n=readPosIntSpace();
		k=readPosLongLn();
		sm+=n;
		assert(1<=sm && sm<=100000);
		assert(1ll<=k && k<=100000000000000ll);
		for(int i=0;i<n;i++){
			c[i]=readPosIntSpace();
			d[i]=readPosIntLn();
			assert(1<= c[i] && c[i]<=1000000000);
			assert(1<= d[i] && d[i]<=1000000000);

			//cin>>c[i]>>d[i];
		}
		Gauss forward;
		stack<Gauss> backward;
		int cur=0;
		long long sm=0;
		int bst=0;
		for(int i=0;i<n;i++){
			if(cur<i){
				forward=Gauss();
				sm=0;
				cur=i;
			}
			while(cur<n && sm + c[cur] <= k){
				forward.add(d[cur]);
				sm+=c[cur];
				cur++;
			}
			Gauss topBackward;
			if(!backward.empty()){
				topBackward=backward.top();
			}
			bst=max(bst,Merge(topBackward,forward).getMax());
			if(backward.empty()){
				Gauss c;
				for(int j=cur-1;j>=i;j--){
					c.add(d[j]);
					backward.push(c);
				}
				forward=Gauss();
			}
			if(cur != i)
				backward.pop();
			sm -= c[i];
		}
		cout<<bst<<endl;
	}
}