#include<cmath>

#include<stack>

#include<queue>

#include<cstdio>

#include<cctype>

#include<vector>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

using namespace std;

typedef long long ll;

const ll INF=1e18;

const int N=2e5+;

inline int read(){

    int X=,w=;char ch=;

    while(!isdigit(ch)){w|=ch=='-';ch=getchar();}

    while(isdigit(ch))X=(X<<)+(X<<)+(ch^),ch=getchar();

    return w?-X:X;

}

struct node{

    int to,nxt,w;

}e[N*];

int n,m,cnt,head[N];

ll dis[][N];

bool vis[N];

queue<int>q;

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

    e[++cnt].to=v;e[cnt].w=w;e[cnt].nxt=head[u];head[u]=cnt;

}

int bfs(int s,int on){

    for(int i=;i<=n;i++)dis[on][i]=INF;

    dis[on][s]=;vis[s]=;q.push(s);

    while(!q.empty()){

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

    for(int i=head[u];i;i=e[i].nxt){

        int v=e[i].to,w=e[i].w;

        if(dis[on][v]>dis[on][u]+w){

        dis[on][v]=dis[on][u]+w;

        if(vis[v])continue;

        vis[v]=;q.push(v);

        }

    }

    vis[u]=;

    }

    ll maxn=;int id;

    for(int i=;i<=n;i++){

    if(maxn<dis[on][i]){

        maxn=dis[on][i];id=i;

    }

    }

    return id;

}

int main(){

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

    for(int i=;i<=m;i++){

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

    add(u,v,w);add(v,u,w);

    }

    int a,b;

    a=bfs(,);b=bfs(a,);bfs(b,);

    ll ans=;

    for(int i=;i<=n;i++){

    ans=max(ans,min(dis[][i],dis[][i]));

    }

    printf("%lld\n",ans+dis[][b]);

    return ;

}