#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef long long ll;

template <typename T>
struct LazySegmentTree {
    int n;
    T unit;
    vector<T> node, lazy;
    vector<bool> lazyFlag;

    T calc(T a, T b){
        T ans;
        //cout << a << b << ' ';
        ans = max(a, b); //適宜変える
        return ans;
    }

    T lazyEvaluateNode(T node, T lazy){
        return node+lazy; //適宜変える
    }

    T clearLazy(){
        return 0; //適宜変える
    }

    LazySegmentTree(vector<T> v, T UNIT) {
        int sz = (int)v.size();
        unit = UNIT;
        n = 1; while(n < sz) n *= 2;
        node.resize(2*n-1, 0);
        lazy.resize(2*n-1, 0);
        lazyFlag.resize(2*n-1, false);

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

    void lazyEvaluate(int k, int l, int r) {
        if(lazyFlag[k]) {
            node[k] = lazyEvaluateNode(node[k], lazy[k]);
            if(r - l > 1) {
                lazy[k*2+1] = lazyEvaluateNode(lazy[k*2+1], lazy[k]);
                lazy[k*2+2] = lazyEvaluateNode(lazy[k*2+2], lazy[k]);
                lazyFlag[k*2+1] = lazyFlag[k*2+2] = true;
            }
            lazyFlag[k] = false;
            lazy[k] = clearLazy();
        }
    }

    //k番目の値(0-indexed)をaに変更
    // void update_node(int k, T a){
    //     k += n-1;
    //     node[k] = a;
    //     while(k > 0){
    //         k = (k-1)/2;
    //         node[k] = calc(node[k*2+1], node[k*2+2]);
    //     }
    // }


    //[a, b)
    //区間[a, b]への更新に対してはupdate(a, b+1, x)と呼ぶ
    void update(int a, int b, T x, int k=0, int l=0, int r=-1) {
        if(r < 0) r = n;
        lazyEvaluate(k, l, r);
        if(b <= l || r <= a) return;
        if(a <= l && r <= b) {
            lazy[k] += x;
            lazyFlag[k] = true;
            lazyEvaluate(k, l, r);
        }
        else {
            update(a, b, x, 2*k+1, l, (l+r)/2);
            update(a, b, x, 2*k+2, (l+r)/2, r);
            node[k] = calc(node[2*k+1], node[2*k+2]);
        }
    }

    //[a, b)
    //区間[a, b]へのクエリに対してはquery(a, b+1)と呼ぶ
    T query(int a, int b, int k=0, int l=0, int r=-1) {
        if(r < 0) r = n;
        lazyEvaluate(k, l, r);
        if(b <= l || r <= a) return unit;
        if(a <= l && r <= b) return node[k];
        T vl = query(a, b, 2*k+1, l, (l+r)/2);
        T vr = query(a, b, 2*k+2, (l+r)/2, r);
        return calc(vl, vr);
    }
};

typedef pair<ll, ll> P;
vector<P> p[200001];

const ll INF = (ll)1e+15;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int N, M;
    cin >> N >> M;
    for(int i = 0; i < M; i++){
        int l, r;
        ll a;
        cin >> l >> r >> a;
        l--; r--;
        p[r].push_back(P(a, l));
    }
    vector<ll> v(N, -INF);
    
    LazySegmentTree<ll> sgt(v, -INF);
    
    int tmp = 0;
    ll ans = 0;
    for(int i = 0; i < N; i++){
        ll sum = 0;
        for(int j = 0; j < p[i].size(); j++){
            sum += p[i][j].first;
        }
        ll q = max(sgt.query(0, i)+sum, sum);
        ll cur = sgt.query(i, i+1);
        sgt.update(i, i+1, q-cur);
        for(int j = 0; j < p[i].size(); j++){
            int l = p[i][j].second;
            ll a = p[i][j].first;
            sgt.update(l, i, a);
        }
    }
    for(int i = 0; i < N; i++){
        ll q = sgt.query(i, i+1);
        ans = max(ans, q);
        //cout << q << ' ';
    }
    //cout << endl;
    cout << ans << endl;
}

Measured memory_bytes: 22656