#include<cstdio>

#include<queue>

#include<cstring>

#include<iostream>

#include<algorithm>

using namespace std;

const int MAXN = ;

struct node

{

        int to;

        int v;

        int next;

}edge[MAXN*];

int p,len;

int num[MAXN];

int vis[MAXN],pre[MAXN],ind,n;

void add(int x,int y,int z)

{

        edge[ind].to = y;

        edge[ind].v = z;

        edge[ind].next = pre[x];

        pre[x] = ind ++;

}

void bfs(int s)

{

        int i;

        queue<int>q;

        vis[s] = ;

        memset(num,,sizeof(num));

        q.push(s);

        while(!q.empty())

        {

                int temp = q.front();

                q.pop();

                for(i=pre[temp]; i!=-; i=edge[i].next){

                        int t = edge[i].to;

                        if(!vis[t]){

                                num[t] = num[temp] + edge[i].v;

                                //cout<<num[t]<<endl;

                                if(num[t] > len){

                                        len = num[t];

                                        p = t;

                                }

                                vis[t] = ;

                                q.push(t);

                        }

                }

        }

}

int main()

{

        //freopen("data.txt","r",stdin);

        int i,j;

        ind = ;

        memset(pre,-,sizeof(pre));

        int x,y,z;

        while(~scanf("%d%d%d",&x,&y,&z))

        {

                add(x,y,z);

                add(y,x,z);

        }

        memset(vis,,sizeof(vis));

        len = ;

        bfs();

        //cout<<p<<endl;

        memset(vis,,sizeof(vis));

        len = ;

        bfs(p);

        cout<<len<<endl;

        return ;

}