#include<bits/stdc++.h>
#define rep(x,a,b) for(int x=a;x<=b;x++)
#define pre(x,a,b) for(int x=a;x>=b;x--)
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
using namespace std;
const int N = 1e6 + 10;
int n, m;
int v[N], w[N];
bitset<1024>f[2][1024];
void solve()
{   
	cin >> n >> m;
	rep(i, 1, n)
	{
		cin >> v[i] >> w[i];
	}
	rep(i, 0, 1023)
	{
		rep(j, 0, 1)
		f[j][i].reset();
	}
	f[0][0][0] = 1;
	rep(i, 1, n)
	{
		rep(j, 0, 1023)
		{
			f[1][j] = f[0][j];
			f[1][j] |= (f[0][j ^ w[i]] << v[i]);
		}
		rep(j, 0, 1023)
		{
			f[0][j] = f[1][j];
		}
	}
	int ans = -1;
	rep(i, 0, 1023) if(f[1][i][m]) ans = i;
	cout << ans << endl;
}
int main()
{
    IOS;
	int _;
	_ = 1;
	cin >> _;
	while(_--)
	{
	    solve();
	}
	return 0;
}