#include <bits/stdc++.h>

using namespace std;

#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(n);i++)
#define rep1(i,n) for(int i=1;i<=(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = 1e18;
//const ll MOD = 1000000007;
//const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout<<setprecision(15)<< fixed<<p<<endl;
int dx[4] = { 1,0, -1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
//#define mp make_pair

class LazySegmentTree {
public:
	int n;
	vl node, lazy;
	bool ismax; //trueなら最大値、falseなら最小値

	LazySegmentTree(vl a, bool _ismax) {
		ismax = _ismax;
		int _n = a.size();
		n = 1; while (n < _n) n *= 2;
		node.resize(2 * n - 1);
        fill(all(node), INF * (1 - (int)ismax * 2));
		lazy.resize(2 * n - 1, 0);
		for (int i = 0; i < _n; i++) node[i + n - 1] = a[i];
		for (int i = n - 2; i >= 0; i--) {
			if (ismax) node[i] = max(node[i * 2 + 1], node[i * 2 + 2]);
			else node[i] = min(node[i * 2 + 1], node[i * 2 + 2]);
		}
	}

	// k番目のノードについて遅延評価を行う
	inline 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, ll x, int k, int l, int r) {
		// k 番目のノードに対して遅延評価を行う
		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);
			if (ismax) node[k] = max(node[2 * k + 1], node[2 * k + 2]);
			else node[k] = min(node[2 * k + 1], node[2 * k + 2]);
		}
	}

	ll getmax(int a, int b, int k, int l, int r) {
		eval(k, l, r);
		if (b <= l || r <= a) return (ismax ? -INF : INF);
		if (a <= l && r <= b) return node[k];
		ll resl = getmax(a, b, 2 * k + 1, l, (l + r) / 2);
		ll resr = getmax(a, b, 2 * k + 2, (l + r) / 2, r);
		if (ismax) return max(resl, resr);
		else return min(resl, resr);
	}

  void debug(int n) {
    rep (i, n) {
      cout << getmax(i, i + 1, 0, 0, n) << " ";
    }
    cout << endl;
  }
};


int main() {
  int n, m;
  cin >> n >> m;
  vector<pair<pii, ll> > rla(m);
  rep (i, m) {
    int l, r;
    ll a;
    cin >> l >> r >> a;
    l--; r--;
    rla[i] = make_pair(pii(r, l), a);
  }
  sort(all(rla));
  //DEBUG_VEC(rla);
  LazySegmentTree lst(vl(n + 1), true);
  int j = 0;
  rep (i, n) {
    //lst.debug(n + 1);
    //DEBUG(i);
    ll ma = lst.getmax(0, i + 1, 0, 0, lst.n);
    //DEBUG(ma);
    lst.add(i + 1, i + 2, ma, 0, 0, lst.n);
    while (j < m && rla[j].first.first ==  i) {
      int l = rla[j].first.second, r = rla[j].first.first;
      ll a = rla[j].second;
      //DEBUG(l); DEBUG(r);
      lst.add(l + 1, r + 2, a, 0, 0, lst.n);
      j++;
    }
  }
  cout << lst.getmax(0, n + 1, 0, 0, lst.n) << endl;
}
  


Measured memory_bytes: 13184