#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;}