//Alhamdulillah
//Md. Masrur Saqib-RUET-1803
//Created on 06-09-2019 11.30

#include<bits/stdc++.h>
#define ll long long
#define pb push_back
#define dd double
#define endl "\n"

using namespace std;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    ll n, m,a,b,lar=0,k;
    cin >> n >> m;
    vector<ll> ara(n);
    for(ll i=0; i<m ; i++){
        cin >> a >> b >> k;
        a--;
        b--;
        for(ll j = a; j<=b ; j++){
            ara[j] += k;
            //cout << "hi" <<endl;
        }
    }
    for(ll i = 0; i<n ; i++){
        lar = (lar>ara[i])?lar:ara[i];
    }
    cout << lar << endl;

    return 0;
}