// cách đệ quy
/*
#include <bits/stdc++.h>
#define int long long
#define MOD 1000000007
using namespace std;
typedef pair<int,int> ii;
typedef vector<ii> viii;
const int N = 100005;

int n,m;
viii a[N];
vector<int> f;
int maxx = 0;

int calc(int u)
{
    if (f[u] != -1) return f[u];
    f[u] = 0;
    for(int i=0; i<a[u].size(); ++i)
    {
        int v = a[u][i].second;
        f[u] = max(f[u], calc(v) + a[u][i].first) % MOD;
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    freopen("maxpdag.inp","r",stdin);
    cin >> n >> m;
    f.resize(n+1,-1);
    for(int i=1; i<=m; ++i)
    {
        int u,v,z;
        cin >> u >> v >> z;
        a[u].push_back(ii(z,v));
    }
    for(int i=1; i<=n; ++i)
    {
        f[i] = calc(i);
    }
    for(int i=1; i<=n; ++i)
    {
        //cout << f[i] << endl;
        maxx = max(maxx,f[i]);
    }
    cout << maxx;
    return 0;
}
*/

// cách topo
#include <bits/stdc++.h>
#define int long long
#define MOD 1000000007
#define TR(k1,k2) for(__typeof((k2).begin()) k1=(k2).begin();k1!=(k2).end();++k1)
using namespace std;
typedef pair<int,int> ii;
typedef vector<ii> vii;
const int N = 100005;

int n,m,d[N];
vector<int> b(N,0);
queue<int> q;
vii a[N];

void sol()
{
    while (q.size())
    {
        int u = q.front();
        q.pop();
        TR(v,a[u])
        {
            if(d[v->second]<d[u] + v->first) d[v->second]=(d[u]+v->first);
            --b[v->second];
            if (!b[v->second]) q.push(v->second);
        }
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    freopen("maxpdag.inp","r",stdin);
    int maxx = 0;
    cin >> n >> m;
        int u,v,z;
    for(int i=1; i<=m; ++i)
    {
        cin >> u >> v >> z;
        a[u].push_back(ii(z,v));
        b[v]++;
    }
    for(int i=1; i<=n; ++i) {
            if (!b[i]) q.push(i);
    }
    sol();
    for(int i=1; i<=n; ++i)
    {
        maxx = max(maxx,d[i]);
    }
    cout << maxx;
    return 0;
}