# include <cstdio>

# include <cstring>

# include <cstdlib>

# include <iostream>

# include <vector>

# include <queue>

# include <stack>

# include <map>

# include <set>

# include <cmath>

# include <algorithm>

using namespace std;

# define lowbit(x) ((x)&(-x))

# define pi 3.1415926535

# define eps 1e-

# define MOD

# define INF

# define mem(a,b) memset(a,b,sizeof(a))

# define FOR(i,a,n) for(int i=a; i<=n; ++i)

# define FO(i,a,n) for(int i=a; i<n; ++i)

# define bug puts("H");

# define lch p<<,l,mid

# define rch p<<|,mid+,r

# define mp make_pair

# define pb push_back

typedef pair<int,int> PII;

typedef vector<int> VI;

# pragma comment(linker, "/STACK:1024000000,1024000000")

typedef long long LL;

int Scan() {

    int res=, flag=;

    char ch;

    if((ch=getchar())=='-') flag=;

    else if(ch>=''&&ch<='') res=ch-'';

    while((ch=getchar())>=''&&ch<='')  res=res*+(ch-'');

    return flag?-res:res;

}

void Out(int a) {

    if(a<) {putchar('-'); a=-a;}

    if(a>=) Out(a/);

    putchar(a%+'');

}

const int N=;

//Code begin...

struct Edge{int p, next, w;}edge[N<<];

int head[N], cnt=;

LL dis[N], dist[N];

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

    edge[cnt].p=v; edge[cnt].w=w; edge[cnt].next=head[u]; head[u]=cnt++;

}

void dfs(int x, int fa){

    for (int i=head[x]; i; i=edge[i].next) {

        int v=edge[i].p;

        if (v==fa) continue;

        dis[v]=dis[x]+edge[i].w;

        dfs(v,x);

    }

}

int main ()

{

    int n, m, u, v, w;

    LL ans=;

    scanf("%d%d",&n,&m);

    while (m--) scanf("%d%d%d",&u,&v,&w), add_edge(u,v,w), add_edge(v,u,w);

    dfs(,);

    int ma=;

    FOR(i,,n) if(dis[ma]<dis[i]) ma=i;

    mem(dis,); dfs(ma,);

    ma=;

    FOR(i,,n) {

        dist[i]=dis[i];

        if (dis[ma]<dis[i]) ma=i;

    }

    mem(dis,); dfs(ma,);

    FOR(i,,n) ans=max(ans,dist[ma]+min(dis[i],dist[i]));

    printf("%lld\n",ans);

    return ;

}