#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <queue>
#include <cmath>
#include <stack>
#include <map>
#include <set>
#include <deque>
#include <cstring>
#include <functional>
#include <climits>
#include <list>
#include <ctime>
#include <complex>

#define F1(x,y,z) for(int x=y;x<z;x++)
#define F2(x,y,z) for(int x=y;x<=z;x++)
#define F3(x,y,z) for(int x=y;x>z;x--)
#define F4(x,y,z) for(int x=y;x>=z;x--)
#define pb push_back
#define LL long long
#define co complex<double>
 
#define MAX 100005
#define AMAX 1500
#define MOD 1000000007

#define f(c,d) ((1<<(c))*(d))

using namespace std;

int t,n,m,ta,tb,tc;
vector<int> va[MAX*3],vb[MAX*3];
bool v[MAX*3];

void dfs(int a){
    v[a]=1;
    tc++;
    F1(b,0,va[a].size())if(vb[a][b]&(1<<tb))if(!v[va[a][b]])dfs(va[a][b]);
}

int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        F2(a,1,n){
            va[a].clear();
            vb[a].clear();
        }
        while(m--){
            scanf("%d%d%d",&ta,&tb,&tc);
            va[ta].pb(tb);
            vb[ta].pb(tc);
            va[tb].pb(ta);
            vb[tb].pb(tc);
        }
        ta=0;
        for(tb=29;tb>=0;tb--){
            tc=0;
            memset(v,0,sizeof(v));
            dfs(1);
            if(tc==n)ta+=1<<tb;
        }
        printf("%d\n",ta);
    }
    //system("pause");
}