#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

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

    int n, q;
    if (!(cin >> n >> q)) return 0;

    vector<long long> diff(n + 2, 0);
    while (q--) {
        int l, r;
        long long v;
        cin >> l >> r >> v;
        diff[l] += v;
        diff[r + 1] -= v;
    }

    long long max_val = 0, cur = 0;
    for (int i = 1; i <= n; ++i) {
        cur += diff[i];
        max_val = max(max_val, cur);
    }

    cout << max_val << "\n";
    return 0;
}