#include<cstdio>

#include<cstring>

#include<cctype>

#include<algorithm>

using namespace std;

#define rep(i,s,t) for(int i=s;i<=t;i++)

#define dwn(i,s,t) for(int i=s;i>=t;i--)

#define clr(x,c) memset(x,c,sizeof(x))

int read(){

	int x=0;char c=getchar();

	while(!isdigit(c)) c=getchar();

	while(isdigit(c)) x=x*10+c-'0',c=getchar();

	return x;

}

const int nmax=5e4+5;

const int inf=0x7f7f7f7f;

struct node{

	int u,v,d;

	node(int u,int v,int d):u(u),v(v),d(d){};

	node(){};

	bool operator<(const node&rhs)const{

	  return d<rhs.d;}

};

node ns[nmax];

void maxs(int &a,int b){

	if(a<b) a=b;

}

int g[nmax],dp[nmax];

int main(){

	int n=read(),m=read(),u,v,d;

	rep(i,1,m) ns[i].u=read(),ns[i].v=read(),ns[i].d=read();

	sort(ns+1,ns+m+1);

	int last=0;

	rep(i,1,m){

		if(i==m||ns[i].d<ns[i+1].d){

			rep(j,last+1,i) g[ns[j].u]=dp[ns[j].u],g[ns[j].v]=dp[ns[j].v];

			rep(j,last+1,i){

				maxs(dp[ns[j].u],g[ns[j].v]+1);

				maxs(dp[ns[j].v],g[ns[j].u]+1);

			}

			last=i;

		}

	}

	int ans=0;

	rep(i,0,n-1) maxs(ans,dp[i]);

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

	return 0;

}