//#include <cmath>
#include <cstdio>
//#include <cstring>
//#include <iostream>
//#include <algorithm>
//#define LL  long long
//#define INF 1000000007
//------------------------------------------------------------
struct P{
    int a;
    int b;
    int c;
}    e[400000],d[400000];
//------------------------------------------------------------
//void Max(int &num1,int num2) { if (num1<num2) num1=num2; }
//void Min(int &num1,int num2) { if (num1>num2) num1=num2; }
//int  Min(int  num1,int num2) { return num1<num2? num1 :num2;}
//------------------------------------------------------------
int  tcase;
int  icase;

int  dm;
int  n,m;
int  i,j,k;
int  fa,fb;

int  far[400000];

int  ned;
int  now;
int  ans;
//------------------------------------------------------------
int getf(int d) { return far[d]==d ? d : far[d]=getf(far[d]); }
//------------------------------------------------------------
int  main( )
{
    for (scanf("%d",&tcase); ++icase<=tcase; )
    {
        //--0 init
        ans=0;
        scanf("%d%d",&n,&m);
        
        
        //--1
        for (i=1; i<=m; i++)
            scanf("%d%d%d",&e[i].a,&e[i].b,&e[i].c);
        
        //--2  1<<29 开始 
        
        
        //--3
        for (now=1<<29; now>=1; now>>=1)
        {
            //--0 init 
            dm=0;
            ned=n-1;
            
            for (i=1; i<=m; i++) if (e[i].c&now)
                d[++dm]=e[i];
            for (i=1; i<=n; i++) far[i]=i;
            
            //--1 check
            for (i=1; i<=dm; i++)
            {
                fa=getf(d[i].a);
                fb=getf(d[i].b);
                if (fa!=fb)
                {
                    far[fa]=fb;
                    ned--;
                }
            }
            
            //--2 
            if (!ned)
            {
                ans+=now;
                for (i=1; i<=dm; i++) e[i]=d[i]; m=dm;
            }
        }
        
        //--3
        if (now) ans=0;
        printf("%d\n",ans);
    }
}