#include <iostream>
#include <vector>

using namespace std;

#define ll long long

int main()
{
    ll n, m, a, b, c;
    cin >> n >> m;

    vector <ll> v(n+1, 0);

    for(int i=0; i<m; i++)
    {
        cin >> a >> b >> c;
        v[a-1] += c;
        v[b] -= c;
    }

    ll maximo = v[0];
    for(int i=1; i<n+1; i++)
        v[i] += v[i-1], maximo = max(maximo, v[i]);

    cout << maximo << endl;

    return 0;
}