1 #include<iostream>
  2 #include<cstdio>
  3 #include<cmath>
  4 #include<cstring>
  5 #include<string>
  6 #include<algorithm>
  7 #include<queue>
  8 #include<vector>
  9 
 10 using namespace std;
 11 typedef long long ll;
 12 const int maxm=5e4*2+2;
 13 const int maxn=1e3+2;
 14 const int inf=0x3f3f3f3f;
 15 int n,m;
 16 struct node
 17 {
 18     int to;
 19     int nxt;
 20     int w;
 21 }e[maxm];
 22 int head[maxn];
 23 int tot;
 24 bool vis[maxn];
 25 int dis[maxn];
 26 int pv[maxn];
 27 int pe[maxn];
 28 typedef pair<int,int> pii;
 29 void init()
 30 {
 31     memset(head,-1,sizeof(head));
 32     tot=0;
 33 }
 34 
 35 void add(int u,int v,int w)
 36 {
 37     e[tot].to=v;
 38     e[tot].w=w;
 39     e[tot].nxt=head[u];
 40     head[u]=tot++;    
 41 }
 42 
 43 int Dij(int x)
 44 {
 45     priority_queue<pii,vector<pii>,greater<pii> >pq;
 46     memset(vis,false,sizeof(vis));
 47     memset(dis,inf,sizeof(dis));
 48     dis[1]=0;
 49     pq.push(make_pair(dis[1],1));
 50 //    pq.push(pii(dis[1],1));
 51     while(!pq.empty())
 52     {
 53         pii cur=pq.top();
 54         pq.pop();
 55         int u=cur.second;
 56         if(vis[u]) continue;
 57         vis[u]=true;
 58         for(int i=head[u];i!=-1;i=e[i].nxt)
 59         {
 60             if(i==x) continue;
 61             int w=e[i].w;
 62             int v=e[i].to;
 63             if(dis[u]+w<dis[v])
 64             {
 65                 dis[v]=dis[u]+w;
 66                 pq.push(make_pair(dis[v],v));
 67                 if(x==-1)
 68                 {
 69                     pv[v]=u;
 70                     pe[v]=i;
 71                 }
 72             }
 73         }
 74     }
 75     return dis[n];
 76 }
 77 
 78 int Solve()
 79 {
 80     if(Dij(-1)==inf)
 81     {
 82         return -1;
 83     }
 84     int ans=0;
 85     for(int i=n;i!=1;i=pv[i])
 86     {
 87         ans=max(ans,Dij(pe[i]));
 88         if(ans==inf)
 89         {
 90             return -1;
 91         }
 92     }
 93     return ans;
 94 }
 95 int main()
 96 {
 97     int T;
 98     scanf("%d",&T);
 99     while(T--)
100     {
101         init();
102         scanf("%d%d",&n,&m);
103         while(m--)
104         {
105             int u,v,w;
106             scanf("%d%d%d",&u,&v,&w);
107             add(u,v,w);
108             add(v,u,w);
109         }
110         int ans=Solve();
111         printf("%d\n",ans);
112     }
113     return 0;
114 }