//By TOP
#include <iostream>
#include <algorithm>
#include <cstring>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <list>
#include <unordered_set>
#include <cmath>
#include <bits/stdc++.h>
#include <deque>
#include <vector>
#include <utility>
using namespace std;
#define int long long
typedef pair<int,int> PII;
#define OO 0x3f3f3f3f
#define rd read()
#define mem(a,b) memset(a,b,sizeof a)
#define ios ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define v1 priority_queue<int,vector<int>,greater<int> > v 
#define v2 priority_queue<int,vector<int>,less<int> > v 
#define debug(a) cout << a << "\n"
const int N = 2000010;
int a[N];
int n;
int tr[N];
/*void build(int u , int l , int r)
{
	tr[u] = {l , r};
	if(l == r)
	{
		return ;
	}
	int mid = l + r >> 1;
	build(u << 1 , l , mid);
	build(u << 1 | 1 , mid + 1  ,r);
}*/
/*int query(int u , int l , int r)
{
	if(tr[u].l >= l && tr[u].r <= r)
	{
		return tr[u].v;
	}
	int mid = tr[u].l + tr[u].r >> 1;
	int v = 0;
	if(l <= mid)
	{
		v.query(u << 1 , l , r);
	}
	if(r > mid)
	{
		v.query(u << 1 | 1 , l , r);
	}
	return v;
	
}*/
int lowbit(int x)
{
	return x & -x;
}
void add(int x,int c)
{
	for(int i = x ; i <= n ; i += lowbit(i) )
	{
		tr[i] += c;
	}
}
int query(int x)
{
	int res = 0;
	
	for(int i = x ; i ; i -= lowbit(i))
	{
		res += tr[i];
	}
	return res;
	
}
inline int read()
 {
	int x = 0, f = 1;
	char ch = getchar();
	while (ch < '0' || ch > '9') {
		if (ch == '-') f = -1;
		ch = getchar();
	}
	while (ch >= '0' && ch <= '9') {
		x = x * 10 + ch - 48;
		ch = getchar();
	}
	return x * f;
}
bitset<1050> dp[1050] , res[1050];
int v[N];
int w[N];

void solve()
{
	int n , m;
	cin >> n >> m;
	for(int i = 0 ; i <= 1024 ; i ++ )
	{
		dp[i].reset();
	}
	
	for(int i = 1 ; i <= n ; i ++ )
	{
		cin >> v[i] >> w[i];
	}
	dp[0][0] = 1;
	for(int i = 1 ; i <= n ; i ++ )
	{
		for(int j = 1023 ; j >= 0 ; j -- )
		{
			res[j] = dp[j];
		}
		for(int j = 1023 ; j >= 0 ; j -- )
		{
			dp[j] |= res[j ^ w[i]] << v[i];
		}
	}
	int ans = -1;
	for(int i = 0 ; i < 1024 ; i ++ )
	{
		if(dp[i][m])
		{
			ans = i;
		}
	}
	cout << ans << "\n";
	
	
}
signed main()
{
	ios;
	
	int t = 1;
	cin >> t;
	while(t -- )
	{
		solve();
	}
	return 0;
}