#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const ll mod = 1e9+7;

ll modpow(ll n, ll k) {
	ll ans = 1;
	for (; k; n = n * n % mod, k /= 2)
		if (k & 1) ans = ans * n % mod;
	return ans;
}

#define int long long

void solve() {
	int n, m; cin >> n >> m;
	vector<bitset<1024>> dp(1024);
	// dp[xorsum][capacity]

	dp[0][0] = 1;
	while (n--) {
		int v, w; cin >> v >> w;
		for (int i = 0; i < 1024; i++) {
			int j = i^w;
			if (j > i) continue;
			
			bitset<1024> ni = dp[i] | (dp[j] << v);
			bitset<1024> nj = dp[j] | (dp[i] << v);

			dp[i] = ni;
			dp[j] = nj;
		}
	}

	int ans = -1;
	for (int i = 0; i < 1024; i++) {
		if (dp[i][m]) ans = i;
	}
	if (ans == -1) {
		ans = 1;
	}
	cout << ans << '\n';
}

signed main() {
	ios::sync_with_stdio(0); cin.tie(0); 
	
	int t; cin >> t;
	while (t--) {
		solve();
	}

	return 0;
}