#include "iostream"
#include "cstring"
#include "cstdio"
#include "algorithm"
#include "queue"
#include "vector"
#include "queue"
#include "stack"
#include "ctime"
#include "set"
#include "map"
#include "bitset"
using namespace std;
#define fi first
#define se second
#define vi vector<int>
#define pb push_back
#define eb emplace_back
#define pii pair<int,int>
#define mp make_pair
#define rep( i , a , b ) for( int i = (a) , i##end = b ; i <= i##end ; ++ i )
#define per( i , a , b ) for( int i = (a) , i##end = b ; i >= i##end ; -- i )
#define mem( a ) memset( a , 0 , sizeof (a) )
#define all( x ) x.begin() , x.end()
//#define int long long
typedef long long ll;
const int MAXN = 26 + 10;
const int P = 998244353;
int n , m , k;

bitset<1024> dp[1030] , pd[1023];

void solve() {
	cin >> n >> m;
	rep( i , 0 , 1023 ) dp[i].reset( );
	dp[0][0] = 1;
	rep( i , 1 , n ) {
		int v , w;
		scanf("%d%d",&v,&w);
		rep( j , 0 , 1023 ) pd[j] = dp[j];
		rep( j , 0 , 1023 ) dp[j] |= ( pd[j ^ w] << v );
	}
	int res = 0;
	rep( k , 0 , 1023 ) if( dp[k][m] ) res = k;
	cout << res << endl;
}

signed main() {
//	freopen("in","r",stdin);
//	freopen("out","w",stdout);
	int T;cin >> T;while( T-- ) solve();
//	solve();
}