#include<bits/stdc++.h>
using namespace std;
struct node{int x,y,c,next;}a[1100];int len,last[1100];
void ins(int x,int y,int c){len++;a[len]=node{x,y,c,last[x]};last[x]=len;}
int rd[1100],d[1100];
int main()
{
    int n,m;scanf("%d%d",&n,&m);
    memset(rd,0,sizeof(rd));
    len=0;memset(last,0,sizeof(last));
    for(int i=1;i<=m;i++)
    {
        int x,y,c;scanf("%d%d%d",&x,&y,&c);
        ins(x,y,c);rd[y]++;
    }
    memset(d,0,sizeof(d));
    queue<int>Q;
    for(int i=1;i<=n;i++)if(rd[i]==0)Q.push(i),rd[i]=-1;
    while(!Q.empty())
    {
        int x=Q.front();
        for(int k=last[x];k>0;k=a[k].next)
        {
            int y=a[k].y;
            if(d[y]<d[x]+a[k].c)d[y]=d[x]+a[k].c;
            rd[y]--;
            if(rd[y]==0)Q.push(y),rd[y]=-1;
        }
        Q.pop();
    }
    int ans=0;for(int i=1;i<=n;i++)ans=max(ans,d[i]);
    printf("%d\n",ans);
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
struct node{int x,y,c,next;}a[1100];int len,last[1100];
void ins(int x,int y,int c){len++;a[len]=node{x,y,c,last[x]};last[x]=len;}
int rd[1100],d[1100];
int main()
{
    int n,m;scanf("%d%d",&n,&m);
    memset(rd,0,sizeof(rd));
    len=0;memset(last,0,sizeof(last));
    for(int i=1;i<=m;i++)
    {
        int x,y,c;scanf("%d%d%d",&x,&y,&c);
        ins(x,y,c);rd[y]++;
    }
    memset(d,0,sizeof(d));
    queue<int>Q;
    for(int i=1;i<=n;i++)if(rd[i]==0)Q.push(i),rd[i]=-1;
    while(!Q.empty())
    {
        int x=Q.front();
        for(int k=last[x];k>0;k=a[k].next)
        {
            int y=a[k].y;
            if(d[y]<d[x]+a[k].c)d[y]=d[x]+a[k].c;
            rd[y]--;
            if(rd[y]==0)Q.push(y),rd[y]=-1;
        }
        Q.pop();
    }
    int ans=0;for(int i=1;i<=n;i++)ans=max(ans,d[i]);
    printf("%d\n",ans);
    return 0;
}