#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
const ll mod = 1e9 + 7;
const ll INF = 1e18;
//--------------------------------------------------------------------
const ll N = 3e5 + 10;
struct ED {
ll u, v, w;
} ed[N];
vector<pa> g[N];
ll n, m;
namespace sub3 {
bool check() {
return m == n - 1;
}
ll f[N];
bool dx[N];
pa par[N];
void dfs(ll u, ll p) {
for(auto e : g[u]) {
ll v = e.fi, id = e.se;
if(v == p) continue;
par[v] = {u, id};
f[v] = f[u] + ed[id].w;
dfs(v, u);
}
}
void slove() {
FOR(i, 1, m) {
ll u = ed[i].u, v = ed[i].v, w = ed[i].w;
g[u].push_back({v, i});
g[v].push_back({u, i});
}
dfs(1, 0);
vector<ll> vt;
ll u = n;
while(u != 1) {
ll v = par[u].fi, id = par[u].se;
dx[id] = 1;
u = v;
}
ll ans = f[n];
ll mx = -INF;
FORD(i, m, 1) {
if(dx[i]) {
ans = max(ans, f[n] + mx);
}
mx = max(ed[i].w, mx);
}
cout << ans;
}
}
namespace sub1 {
bool check() {
return n <= 2000 && m <= 2000;
}
const ll N = 2003;
ll d[N];
void DJK() {
priority_queue<pa, vector<pa>, greater<pa>> q;
q.push({0, 1});
fill(d + 1, d + n + 1, INF);
d[1] = 0;
while(!q.empty()) {
ll u = q.top().se, du = q.top().fi;
q.pop();
if(du != d[u]) continue;
for(auto e : g[u]) {
ll v = e.fi, w = ed[e.se].w;
if(d[v] > d[u] + w) {
d[v] = d[u] + w;
q.push({d[v], v});
}
}
}
}
void slove() {
FOR(i, 1, m) {
ll u = ed[i].u, v = ed[i].v, w = ed[i].w;
g[u].push_back({v, i});
g[v].push_back({u, i});
}
DJK();
ll ans = d[n];
ll mx = ed[m].w;
FORD(i, m - 1, 1) {
ed[i].w = ed[i].w + mx;
DJK();
ans = max(ans, d[n]);
ed[i].w = ed[i].w - mx;
mx = max(ed[i].w, mx);
}
cout << ans;
}
}
namespace subend {
ll c[N];
ll d_1[N], d_n[N];
ll num[N], low[N], timedfs;
bool used[N], bridge[N];
void DJK(ll s, ll d[]) {
priority_queue<pa, vector<pa>, greater<pa>> q;
q.push({0, s});
fill(d + 1, d + n + 1, INF);
d[s] = 0;
while(!q.empty()) {
ll du = q.top().fi, u = q.top().se;
q.pop();
if(du != d[u]) continue;
for(auto e : g[u]) {
ll v = e.fi, w = ed[e.se].w;
if(d[v] > d[u] + w) {
d[v] = d[u] + w;
q.push({d[v], v});
}
}
}
}
void dfs(ll u) {
num[u] = low[u] = ++timedfs;
for(auto e : g[u]) {
ll v = e.fi, id = e.se;
if(used[id]) continue;
used[id] = 1;
if(!num[v]) {
dfs(v);
if(low[v] == num[v] && num[v] <= num[n]) {
bridge[id] = 1;
}
low[u] = min(low[v], low[u]);
}
else {
low[u] = min(low[u], num[v]);
}
}
}
bool check(ll L) {
FOR(i, 1, n) {
num[i] = low[i] = 0;
}
timedfs = 0;
FOR(i, 1, m) {
used[i] = 0;
bridge[i] = 0;
ll u = ed[i].u, v = ed[i].v, w = ed[i].w;
if(!(d_1[u] + d_n[v] + w < L || d_1[v] + d_n[u] + w < L)) {
used[i] = 1;
}
}
dfs(1);
FOR(i, 1, m - 1) {
ll u = ed[i].u, v = ed[i].v, w = ed[i].w;
if(bridge[i]) {
if(min(d_1[v] + d_n[u], d_1[u] + d_n[v]) + w + c[i] >= L) {
return true;
}
}
}
return false;
}
void slove() {
FOR(i, 1, m) {
ll u = ed[i].u, v = ed[i].v, w = ed[i].w;
g[u].push_back({v, i});
g[v].push_back({u, i});
}
ll mx = ed[m].w;
c[m] = -INF;
FORD(i, m - 1, 1) {
c[i] = mx;
mx = max(mx, ed[i].w);
}
DJK(1, d_1);
DJK(n, d_n);
ll l = d_1[n] + 1, r = mx + l;
ll ans = d_1[n];
while(l <= r) {
ll mid = l + r >> 1;
if(check(mid)) {
l = mid + 1;
ans = mid;
}
else r = mid - 1;
}
cout << ans << '\n';
}
}
void hbmt() {
cin >> n >> m;
FOR(i, 1, m) {
ll u, v, w;
cin >> u >> v >> w;
ed[i] = {u, v, w};
}
// if(sub1::check()) return sub1::slove();
// if(sub3::check()) return sub3::slove();
return subend::slove();
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
#define NAME "hbmt"
if(fopen(NAME".inp", "r")) {
freopen(NAME".inp", "r", stdin);
freopen(NAME".out", "w", stdout);
}
//int t;cin>>t;while(t--)
hbmt();
return 0;
}
/*
6 8
5 6 2
3 1 4
1 2 2
6 2 3
5 3 3
3 2 1
4 6 3
2 4 2
ans : 8
7 6
2 1 4
1 3 3
4 5 4
5 7 3
4 6 2
1 4 0
ans = 10
5 5
4 3 3
1 4 4
3 1 3
4 5 2
2 3 1
ans - 8
*/
