#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cmath>
#include<map>
#define ll long long
using namespace std;
const int maxn=500010,inf=1e9;
struct poi{int too,dis,pre;}e[maxn];
int n,m,x,y,z,tot,ans;
int last[maxn],dp[maxn];
void read(int &k)
{int f=1;k=0;char c=getchar();while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar();while(c<='9'&&c>='0')k=k*10+c-'0',c=getchar();k*=f;
}
void add(int x,int y,int z){e[++tot].too=y;e[tot].dis=z;e[tot].pre=last[x];last[x]=tot;}
int dfs(int x,int fa)
{if(dp[x])return dp[x];dp[x]=1;for(int i=last[e[x].too];i;i=e[i].pre)if(i!=fa&&e[i].dis>e[x].dis)dfs(i,x),dp[x]=max(dp[x],dp[i]+1);return dp[x];
}
int main()
{read(n);read(m);for(int i=1;i<=m;i++)read(x),read(y),read(z),add(x,y,z),add(y,x,z);for(int i=1;i<=tot;i++)if(!dp[i])dfs(i,0);for(int i=1;i<=tot;i++)ans=max(ans,dp[i]);printf("%d\n",ans);return 0;
}

#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cmath>
#include<map>
#define ll long long
using namespace std;
const int maxn=500010,inf=1e9;
struct poi{int x,too,dis;}e[maxn];
int n,m,x,y,z,ans,last;
int g[maxn],f[maxn];
void read(int &k)
{int f=1;k=0;char c=getchar();while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar();while(c<='9'&&c>='0')k=k*10+c-'0',c=getchar();k*=f;
}
bool cmp(poi a,poi b){return a.dis<b.dis;}
int main()
{read(n);read(m);for(int i=1;i<=m;i++)read(x),read(y),read(z),e[i].x=x,e[i].too=y,e[i].dis=z;sort(e+1,e+1+m,cmp);last=1;for(int i=1;i<=m;i++)if(i==m||e[i].dis<e[i+1].dis){for(int j=last;j<=i;j++)g[e[j].too]=f[e[j].too],g[e[j].x]=f[e[j].x];for(int j=last;j<=i;j++)f[e[j].too]=max(f[e[j].too],g[e[j].x]+1),f[e[j].x]=max(f[e[j].x],g[e[j].too]+1);last=i+1;}for(int i=0;i<n;i++)ans=max(ans,f[i]);printf("%d\n",ans);return 0;
}