#include <cstdio>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <cctype>
#include <utility>
#include <queue>
#include <cmath>
#include <complex>
using namespace std;

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
typedef double DB;

#define pb push_back
#define mset(a, b) memset(a, b, sizeof a)
#define all(x) (x).begin(), (x).end()
#define bit(x) (1 << (x))
#define bitl(x) (1LL << (x))
#define sqr(x) ((x) * (x))
#define sz(x) ((int)(x.size()))
#define counti(x) (__builtin_popcount(x))
#define clz(x) (__builtin_clz(x))
#define ctz(x) (__builtin_ctz(x))
#define countl(x) (__builtin_popcountll(x))
#define rep(i, n) for (int (i) = 0; (i) < (int)(n); ++(i))
#define Error(x) cout << #x << " = " << endl
#define X first
#define Y second
  
template <typename T, typename U> 
inline void chkmax(T& x, U y) {
    if (x < y) x = y;
}
  
template <typename T, typename U>
inline void chkmin(T& x, U y) {
    if (y < x) x = y;
}
#define MX 312345
struct Edge {
  int u, v, w;
  void input() {
    scanf("%d%d%d", &u, &v, &w);
  }
}e[MX];
int n, m;
int root[MX];
int Find_root(int u) {
  return root[u] == u ? u : root[u] = Find_root(root[u]);
}
int solve() {
  int ret = 0;
  for (int i = 30; i >= 0; i--) {
    int cnt = 0;
    ret |= bit(i);
    for (int j = 1; j <= n; j++) root[j] = j;
    for (int j = 0; j < m; j++) if ((ret & e[j].w) == ret) {
      int u = e[j].u, v = e[j].v;
      u = Find_root(u), v = Find_root(v);
      if (u != v) {
        root[u] = v;
        cnt++;
      }
    }
    if (cnt != n - 1) {
      ret ^= bit(i);
    }
  }
  
  return ret;
}
int main() {
    
  int Tcase;
  for (scanf("%d", &Tcase); Tcase--;) {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
      e[i].input();
    }  
    printf("%d\n", solve());
  }
  return 0;
}