#include <bits/stdc++.h>
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define st first
#define nd second
using namespace std;
typedef long long ll;
const int mod = 1e9 + 7;
const int N = 1e6 + 5;
int pre[N], suf[N], par[N], s[N];
vector<int> adj[N];

int qry(int x) { return x == par[x] ? x : qry(par[x]); }

void join(int x, int y) {
  x = qry(x);
  y = qry(y);
  if (s[x] > s[y])
    swap(x, y);
  if (x != y) {
    adj[x].push_back(y), adj[y].push_back(x);
    s[y] += s[x];
    par[x] = y;
  }
}

void dfs(int u, int f, int w) {
  (f == 1 ? pre : suf)[u] = w;
  for (int v: adj[u]) {
    if (f == 1 && pre[v] != 0 || f == 2 && suf[v] != 0)
      continue;
    dfs(v, f, w);
  }
}

int main() {
  ios_base::sync_with_stdio(false); cin.tie(0);
  int n, m; cin >> n >> m;
  vector<array<int, 3>> arr;
  for (int i = 0; i < m; i++) {
    int u, v, w; cin >> u >> v >> w;
    arr.push_back({w, u, v});
  }
  iota(par, par + n + 1, 0);
  fill(s, s + n + 1, 1);
  sort(all(arr));
  for (auto [w, u, v]: arr) {
    if (qry(u) == qry(1) || qry(v) == qry(1))
      dfs(qry(u) == qry(1) ? v : u, 1, w);
    if (qry(u) == qry(n) || qry(v) == qry(n))
      dfs(qry(u) == qry(n) ? v : u, 2, w);
    join(u, v);
  }
  int ans = 2'000'000'000;
  for (auto [w, u, v]: arr) {
    // cout << u << " " << v << " " << pre[u] << " " << suf[v] << endl;
    // cout << v << " " << u << " " << pre[v] << " " << suf[u] << endl;
    vector<int> tmp = {pre[u], suf[v], w};
    sort(all(tmp));
    ans = min(ans, tmp[1] + tmp[2]);
    tmp = {pre[v], suf[u], w};
    sort(all(tmp));
    ans = min(ans, tmp[1] + tmp[2]);
  }
  cout << ans << "\n";
}