// start time : 15 : 17

#include <bits/stdc++.h>

#define rep(i,l,r) for (int i = l; i <= r; i++)
#define per(i,r,l) for (int i = r; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define mp std::make_pair
#define gin std::cin
#define prt std::cout
#define edl std::endl

namespace Main {
  const int N = 3e5 + 5;
  int n,m,dist1[N],distn[N],val[N],val1[N],valn[N],fa[N];
  std::vector<std::pair<int,int>> G[N];
  struct Edge {
    int u,v,w;
    Edge() {}
    Edge(int _u,int _v,int _w) {
      u = _u; v = _v; w = _w;
    }
    bool operator<(const Edge &B) const {
      return w < B.w;
    }
  } ;
  int get(int x) { return fa[x] == x ? x : fa[x] = get(fa[x]); }
  void merge(int x,int y) {
    fa[get(x)] = fa[get(y)];
  }
  void dfs1(int x,int fa) {
    for (auto e : G[x]) {
      int v = e.first;
      if (v == fa) continue;
      dist1[v] = std::max(dist1[x],e.second);
      val1[v] = std::max(val1[x],val[e.second]);
      dfs1(v,x);
    }
  }
  void dfs2(int x,int fa) {
    for (auto e : G[x]) {
      int v = e.first;
      if (v == fa) continue;
      distn[v] = std::max(distn[x],e.second);
      valn[v] = std::max(valn[x],val[e.second]);
      dfs2(v,x);
    }
  }
  std::vector<Edge> edges;
  void main() {
    scanf("%d%d",&n,&m);
    rep(i,1,m) {
      int u,v,w;
      scanf("%d%d%d",&u,&v,&w);
      edges.push_back(Edge(u,v,w));
    }
    rep(i,1,n) {
      fa[i] = i;
    }
    std::sort(edges.begin(),edges.end());
    int cur = 0;
    for (auto e : edges) {
      int u = e.u,v = e.v,w = e.w; ++ cur; val[cur] = w;
      if (get(u) == get(v)) continue;
      merge(u,v); G[u].push_back({v,cur}); G[v].push_back({u,cur});
    }
    dfs1(1,-1); dfs2(n,-1);
    int ans = INT_MAX;
    cur = 0;
    for (auto e : edges) {
      ++ cur;
      int u = e.u,v = e.v,w = e.w;
      if (dist1[u] < cur && distn[v] < cur) {
        ans = std::min(ans,w + val1[u] + valn[v]);
      }
      if (dist1[v] < cur && distn[u] < cur) {
        ans = std::min(ans,w + val1[v] + valn[u]);
      }
    }
    prt << ans;
  }
} signed main() { Main::main(); return 0; }