#include <bits/stdc++.h>
using namespace std;
const long long INF = 0x3f3f3f3f3f3f3f3f, N = 2e5 + 10;
long long n, m;
struct node
{
    long long y;
    long long z;
} ll;
vector<node> G[N];
long long sh[N], dfs1shen1, dfs1shen2 = -INF;
void dfs(long long s, long long fa, long long zz, bool blogg)
{
    if (!blogg)
        sh[s] = sh[fa] + zz;
    if (sh[s] >= dfs1shen2)
    {
        dfs1shen1 = s;
        dfs1shen2 = sh[s];
    }
    for (auto v : G[s])
    {
        if (v.y == fa)
            continue;
        dfs(v.y, s, v.z, 0);
    }
}
long long zj1, zj2;

bool vis1[N];
int d1[N];

// 点u, d[u]

struct VNode
{
    int p;
    int d;
    bool operator<(const VNode &b) const
    {
        return d > b.d;
    }
};

void dijkstra1(int s)
{
    priority_queue<VNode> q;
    for (int i = 1; i <= n; i++)
    {
        d1[i] = INF;
    }
    d1[s] = 0;
    q.push({s, 0});
    while (!q.empty())
    {
        int u = q.top().p; // 找到堆顶元素
        q.pop();
        if (vis1[u]) // 如果已经找到了, 就不要再操作了
        {
            continue;
        }
        // 如果已经在S集合中了, 就不要操作了, 只有在T集合中的点, 我们才
        // 拿进去, 然后松弛
        vis1[u] = 1;
        for (auto e : G[u])
        {
            int v = e.y;
            int w = e.z;
            if (vis1[v] == 0 && d1[v] > d1[u] + w)
            {
                d1[v] = d1[u] + w;
                q.push({v, d1[v]});
            }
        }
    }
}

bool vis2[N];
int d2[N];

// 点u, d[u]

void dijkstra2(int s)
{
    priority_queue<VNode> q;
    for (int i = 1; i <= n; i++)
    {
        d2[i] = INF;
    }
    d2[s] = 0;
    q.push({s, 0});
    while (!q.empty())
    {
        int u = q.top().p; // 找到堆顶元素
        q.pop();
        if (vis2[u]) // 如果已经找到了, 就不要再操作了
        {
            continue;
        }
        // 如果已经在S集合中了, 就不要操作了, 只有在T集合中的点, 我们才
        // 拿进去, 然后松弛
        vis2[u] = 1;
        for (auto e : G[u])
        {
            int v = e.y;
            int w = e.z;
            if (vis2[v] == 0 && d2[v] > d2[u] + w)
            {
                d2[v] = d2[u] + w;
                q.push({v, d2[v]});
            }
        }
    }
}

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for (long long i = 1; i <= m; i++)
    {
        long long x, y, z;
        cin >> x >> y >> z;
        ll.y = y;
        ll.z = z;
        G[x].push_back(ll);
        ll.y = x;
        G[y].push_back(ll);
    }
    sh[1] = 1;
    dfs(1, -1, 1145, 1);
    zj1 = dfs1shen1;
    memset(sh, 0, sizeof(sh));
    dfs1shen1 = 0, dfs1shen2 = -INF;

    dfs(zj1, 0, 1145, 1);
    zj2 = dfs1shen1;
    dijkstra1(zj1);
    dijkstra2(zj2);
    long long ans = -INF;
    for (long long i = 1; i <= n; i++)
    {
        if (i == zj1 || i == zj2)
            continue;
        ans = max(ans, d1[i] + d2[i] + dfs1shen2);
    }
    cout << ans;
    return 0;
}