#include <iostream>

#include <algorithm>

#include <cstdio>

#include <cstring>

#include <queue>

#include <cmath>

#include <deque>

#include <vector>

using namespace std;

const int maxn = 10008;

const int inf = 0x3ffffff;

struct Node {

    int w, next,to;

    Node (int x = 0, int y = 0,int u = 0 ){

        to = x;w = y;next = u;

    }

}e[maxn*4];

int d[maxn],head[maxn],tot;

void add(int u,int v,int w){

    e[tot] = Node(v,w,head[u]);

    head[u] = tot++;

    e[tot] = Node(u,w,head[v]);

    head[v] = tot++;

}

int BFS(int u) {

    memset(d,-1,sizeof(d));

    d[u] = 0;

    int max_int = 0,id = u;

    queue <int> q;

    q.push(u);

    while(!q.empty()){

        u = q.front();q.pop();

        if(d[u] > max_int) {

            max_int = d[u];

            id = u;

        }

        for(int i=head[u];i!=-1;i=e[i].next){

        if(d[e[i].to] == -1){

                d[e[i].to] = d[u] + e[i].w;

                q.push(e[i].to);

            }

        }

    }

   // cout << id <<endl;

    return id;

}

int main(){

    int u,v,w;    //freopen("input.txt","r",stdin);

    memset(head,-1,sizeof(head));

    tot = 0;

    while(scanf("%d%d%d",&u,&v,&w) == 3)add(u,v,w);

    printf("%d\n",d[BFS(BFS(u))]);

    return 0;

}