#include <queue>

 #include <cstdio>

 #include <cstring>

 #include <iostream>

 using namespace std;

 const int MAXN = ;

 int n, m, cnt, ans, qu, qv;

 int head[MAXN], to[MAXN * MAXN], next[MAXN * MAXN], val[MAXN * MAXN], dis[MAXN], pre[MAXN];

 bool vis[MAXN], flag;

 queue <int> q;

 inline void add(int x, int y, int z)

 {

     to[cnt] = y;

     val[cnt] = z;

     next[cnt] = head[x];

     head[x] = cnt++;

 }

 inline void spfa(int u)

 {

     int i, v;

     while(!q.empty()) q.pop();

     memset(vis, , sizeof(vis));

     memset(dis,  / , sizeof(dis));

     q.push(u);

     dis[u] = ;

     while(!q.empty())

     {

         u = q.front();

         q.pop();

         vis[u] = ;

         for(i = head[u]; i != -; i = next[i])

         {

             v = to[i];

             if((u == qu && v == qv) || (u == qv && v == qu)) continue;

             if(dis[v] > dis[u] + val[i])

             {

                 dis[v] = dis[u] + val[i];

                 if(!flag) pre[v] = u;

                 if(!vis[v])

                 {

                     vis[v] = ;

                     q.push(v);

                 }

             }

         }

     }

 }

 int main()

 {

     int i, x, y, z;

     scanf("%d %d", &n, &m);

     memset(pre, -, sizeof(pre));

     memset(head, -, sizeof(head));

     for(i = ; i <= m; i++)

     {

         scanf("%d %d %d", &x, &y, &z);

         add(x, y, z);

         add(y, x, z);

     }

     spfa();

     flag = ;

     for(i = n; i != -; i = pre[i])

     {

         qu = i;

         qv = pre[i];

         spfa();

         if(dis[n] != ) ans = max(ans, dis[n]);

     }

     printf("%d", ans);

     return ;

 }