#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mk make_pair
#define S second
#define F first
const int N = 3e5 + 5;
vector<pair<int, int>> adj[N];
vector<int> active[N];
vector<tuple<int, int, int>> edges;
vector<bool> vis;
int n, m;
void init(){
    cin >> n >> m;
    vis.assign(n + 1, 0);
    int u, v, w;
    for(int i = 0; i < m; i++){
        cin >> u >> v >> w;
        if(u > v) swap(u, v);
        adj[v].emplace_back(u, w);
        adj[u].emplace_back(v, w);
        edges.emplace_back(w, u, v);
    }
}
vector<int> nw;
void dfs(int v){
     if(vis[v]) return;
   //  cout << "irsen :" << v << endl;
     vis[v] = true;
     nw.push_back(v);
     for(auto u: active[v]){
         if(vis[u]) continue;
         dfs(u);
     }
}
int32_t main(){
     ios::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
     init();
     sort(edges.begin(), edges.end());
     ll ans = 2e9 + 5;
     set<pair<int, int>> s1, s2;
     vector<bool> cnt1(n + 1, 0), cnt2(n + 1, 0);
     cnt1[1] = cnt2[n] = true;
     vis[1] = vis[n] = true;
     int t_mn = 2e9;
     for(auto &[u, w] : adj[1]) {
            if(u == n) ans = w;
            s1.insert({1, u});
     }
     int ih, baga;
     for(auto &[u, _] : adj[n]) s2.insert({u, n});

     for(auto &[weigth, u, v] : edges){
         nw.clear();
       //  cout << "cur edge: " << u << " " << v << endl;
         active[u].pb(v);
         active[v].pb(u);
         if(cnt1[u] || cnt1[v]){
                         dfs(u); dfs(v);
               for(auto new_vert : nw){
                  //  cout << "new :" << new_vert << endl;
                   for(auto &[t, w] : adj[new_vert]){
                       // cout << "temptrul :" << t << endl;
                        baga = min(new_vert, t), ih = max(new_vert, t);
                        if(s2.count({baga, ih})) t_mn = min(t_mn, w);
                        s1.insert({baga, ih});
                  }
                  cnt1[new_vert] = true;
               }

         }else if(cnt2[u] || cnt2[v]){
                      dfs(u); dfs(v);
               for(auto new_vert : nw){
                    // cout << "new :" << new_vert << endl;
                   for(auto &[t, w] : adj[new_vert]){
                        baga = min(new_vert, t), ih = max(new_vert, t);
                       // cout << "temptrul :" << t << endl;
                        if(s1.count({baga, ih})) t_mn = min(t_mn, w);
                        s2.insert({baga, ih});
                  }
                  cnt2[new_vert] = true;
               }
         }
     //    cout << "tmin :" << t_mn << endl;
     //    cout << "cnt1 :\n";
     //    for(int i = 0; i <=n; i++) if(cnt1[i]) cout << i << " ";
      //   cout << endl;
     //    cout << "cnt2 :\n";
    //     for(int i = 0; i <=n; i++) if(cnt2[i]) cout << i << " ";
    //     cout << endl;
   //      cout << endl;


         ans = min((ll)weigth + (ll)t_mn, ans);
     }
     cout << ans << '\n';


}