/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author tatsumack
 */

#include <iostream>
#include <fstream>

#include <iostream>
#include <limits.h>
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>

#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <queue>
#include <unordered_map>
#include <unordered_set>

#define int long long
#define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define REPS(i, n) for (int i = 1, i##_len = (n); i <= i##_len; ++i)
#define FOR(i, a, b) for (int i = (a), i##_len = (b); i <= i##_len; ++i)
#define REV(i, a, b) for (int i = (a); i >= (b); --i)
#define CLR(a, b) memset((a), (b), sizeof(a))
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define INF 1001001001001001001ll
#define fcout cout << fixed << setprecision(12)

using namespace std;

template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template<typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T& t, const V& v) { t = v; }

template<typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T& t, const V& v) {
    for (auto& e:t) fill_v(e, v);
}

typedef pair<int, int> P;

// 区間最大、区間加算
struct LazySegmentTree {
private:
    int n;
    vector<int> node, lazy;

public:
    LazySegmentTree(vector<int> v) {
        int sz = (int) v.size();
        n = 1;
        while (n < sz) n *= 2;
        node.resize(2 * n - 1);
        lazy.resize(2 * n - 1, 0);

        for (int i = 0; i < sz; i++) node[i + n - 1] = v[i];
        for (int i = n - 2; i >= 0; i--) node[i] = max(node[i * 2 + 1], node[i * 2 + 2]);
    }

    void eval(int k, int l, int r) {
        if (lazy[k] != 0) {
            node[k] += lazy[k];
            if (r - l > 1) {
                lazy[2 * k + 1] += lazy[k];
                lazy[2 * k + 2] += lazy[k];
            }
            lazy[k] = 0;
        }
    }

    void add(int a, int b, int x, int k = 0, int l = 0, int r = -1) {
        if (r < 0) r = n;
        eval(k, l, r);
        if (b <= l || r <= a) return;
        if (a <= l && r <= b) {
            lazy[k] += x;
            eval(k, l, r);
        } else {
            add(a, b, x, 2 * k + 1, l, (l + r) / 2);
            add(a, b, x, 2 * k + 2, (l + r) / 2, r);
            node[k] = max(node[2 * k + 1], node[2 * k + 2]);
        }
    }

    int find(int a, int b, int k = 0, int l = 0, int r = -1) {
        if (r < 0) r = n;
        eval(k, l, r);
        if (b <= l || r <= a) return -INF;
        if (a <= l && r <= b) return node[k];
        int vl = find(a, b, 2 * k + 1, l, (l + r) / 2);
        int vr = find(a, b, 2 * k + 2, (l + r) / 2, r);
        return max(vl, vr);
    }
};


class WIntervals {
public:
    void solve(std::istream& cin, std::ostream& cout) {
        int N, M;
        cin >> N >> M;

        vector<int> L(N + 1);
        vector<vector<P>> R(N + 1);
        REP(i, M) {
            int l, r, a;
            cin >> l >> r >> a;
            L[l] += a;
            R[r].push_back({l, a});
        }

        LazySegmentTree seg(vector<int>(N + 2, 0));

        int res = 0;
        FOR(i, 1, N) {
            seg.add(0, i, L[i]);

            int val = seg.find(0, i);
            res = max(res, val);
            seg.add(i, i + 1, val);
            REP(j, R[i].size()) {
                int l = R[i][j].first;
                int a = R[i][j].second;
                seg.add(0, l, -a);
            }
        }
        cout << res << endl;
    }
};


signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    std::istream& in(std::cin);
    std::ostream& out(std::cout);

    WIntervals solver;
    solver.solve(in, out);
    return 0;
}


Measured memory_bytes: 22528