#include <bits/stdc++.h>

using namespace std;

#define int long long

#define rep(i, a, b) for (register int i = (a); i <= (b); i++)

const int inf = 0x3f3f3f3f, maxn = 2e5 + ;

int n, m, ans, tmp, str, end, num_edge = ;

int dis1[maxn], dis2[maxn], head[maxn];

struct node {

    int to, dis, nxt;

}edge[maxn << ];

int MIN(int a, int b) {return a < b ? a : b;}

void origin() {

    memset(dis1, , sizeof(head));

    memset(dis2, , sizeof(head));

    memset(head, -, sizeof(head));

}

int read() {

    int x = , flag = ;

    char ch = ' ';

    while (ch != '-' && (ch < '' || ch > '')) ch = getchar();

    if (ch == '-') {

        flag = ;

        ch = getchar();

    }

    while (ch >= '' && ch <= '') {

        x = (x << ) + (x << ) + ch - '';

        ch = getchar();

    }

    return flag ? -x : x;

}

void addedge(int from, int to, int dis) {

    edge[++num_edge].nxt = head[from];

    edge[num_edge].to = to;

    edge[num_edge].dis = dis;

    head[from] = num_edge;

}

void dfs1(int u, int fa) {

    for (register int i = head[u]; ~i; i = edge[i].nxt) {

        int v = edge[i].to;

        if (v == fa) continue;

        dis1[v] = dis1[u] + edge[i].dis;

        if (dis1[v] > dis1[str]) str = v;

        dfs1(v, u);

    }

}

void dfs2(int u, int fa) {

    for (register int i = head[u]; ~i; i = edge[i].nxt) {

        int v = edge[i].to;

        if (v == fa) continue;

        dis2[v] = dis2[u] + edge[i].dis;

        if (dis2[v] > dis2[end]) end = v;

        dfs2(v, u);

    }

}

void dfs3(int u, int fa) {

    for (register int i = head[u]; ~i; i = edge[i].nxt) {

        int v = edge[i].to;

        if (v == fa) continue;

        dis1[v] = dis1[u] + edge[i].dis;

        dfs3(v, u);

    }

}

void dfs4(int u, int fa) {

    for (register int i = head[u]; ~i; i = edge[i].nxt) {

        int v = edge[i].to;

        if (v == fa) continue;

        dis2[v] = dis2[u] + edge[i].dis;

        dfs4(v, u);

    }

}

void write(int x) {

    if (x < ) {

        putchar('-');

        x = -x;

    }

    if (x > ) write(x / );

    putchar(x %  + '');

}

signed main() {

    origin();

    n = read(), m = read();

    rep(i, , m) {

        int u, v, w;

        u = read(), v = read(), w = read();

        addedge(u, v, w);

        addedge(v, u, w);

    }

    dfs1(, );

    dfs2(str, );

    ans = dis2[end];

    memset(dis1, , sizeof(head));

    memset(dis2, , sizeof(head));

    dfs3(str, );

    dfs4(end, );

    rep(i, , n) {

        int flag = MIN(dis1[i], dis2[i]);

        if (flag > tmp) tmp = flag;

    }

    ans += tmp;

    write(ans);

    return ;

}