#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 5;
int p[N];
vector<int> V[N];

void init(int n){
    for(int i = 0; i < n; i++)p[i] = i, V[i] = vector<int>(1, i);
}
int f(int ind){
    return p[ind] = (ind == p[ind] ? ind : f(p[ind]));
}
vector<int> un(int u, int v, int check){
    u = f(u);
    v = f(v);
    if(u == v)return vector<int>();
    if(V[u].size() < V[v].size())swap(u, v);
    check = f(check);

    vector<int> ret;
    if(u == check)ret = V[v];
    else if(v == check)ret = V[u];

    p[v] = u;
    while(V[v].empty()){
        V[u].push_back(V[v].back());
        V[v].pop_back();
    }
    return ret;
}
int when[2][N];

void solv(int ces){
    int n, m;
    cin >> n >> m;
    vector<tuple<int, int, int>> ed(m);
    for(auto &[d, u, v] : ed){
        cin >> u >> v >> d;
        u--, v--;
    }
    sort(ed.begin(), ed.end());
    init(n);
    memset(when, -1, sizeof when);
    when[0][0] = 0;
    for(auto [d, u, v] : ed){
        auto t = un(u, v, 0);
        for(auto x : t){
//            cout << x << endl;
            when[0][x] = d;
        }
    }

    init(n);
    when[1][n - 1] = 0;
    for(auto [d, u, v] : ed){
        auto t = un(u, v, n - 1);
        for(auto x : t)when[1][x] = d;
    }

//    cout << when[0][1] << ' ' << when[1][3] << endl;
    int ans = 2e9 + 2;
    for(auto [d, u, v] : ed){
        int a = when[0][u], b = when[1][v];
        if(a != -1 && b != -1 && a <= d && b <= d)ans = min(ans, d + max(a, b));
        swap(u, v);
        a = when[0][u], b = when[1][v];
        if(a != -1 && b != -1 && a <= d && b <= d)ans = min(ans, d + max(a, b));
    }

    cout << ans << "\n";
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int tc = 1;
//    cin>>tc;
    for(int ces=1; ces<=tc; ces++){
        solv(ces);
    }

    return 0;
}