#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef double db; 
typedef string str; 
 
typedef pair<int,int> pi;
typedef pair<ll,ll> pl; 
typedef pair<db,db> pd; 
 
typedef vector<int> vi; 
typedef vector<ll> vl; 
typedef vector<db> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 
 
#define mp make_pair 
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend() 
#define rsz resize
#define ins insert 
#define ft front() 
#define bk back()
#define pf push_front 
#define pb push_back
#define eb emplace_back 
#define lb lower_bound 
#define ub upper_bound 
 
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)
 
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5; 
const ll INF = 1e18; 
const ld PI = acos((ld)-1);
const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; 
 
template<class T> bool ckmin(T& a, const T& b) { 
	return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { 
	return a < b ? a = b, 1 : 0; } 
int pct(int x) { return __builtin_popcount(x); } 
int bit(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) 
int cdiv(int a, int b) { return a/b+!(a<0||a%b == 0); } // division of a by b rounded up, assumes b > 0 
 
namespace input {
	template<class T> void re(complex<T>& x);
	template<class T1, class T2> void re(pair<T1,T2>& p);
	template<class T> void re(vector<T>& a);
	template<class T, size_t SZ> void re(array<T,SZ>& a);
 
	template<class T> void re(T& x) { cin >> x; }
	void re(double& x) { string t; re(t); x = stod(t); }
	void re(ld& x) { string t; re(t); x = stold(t); }
	template<class T, class... Ts> void re(T& t, Ts&... ts) { 
		re(t); re(ts...); 
	}
 
	template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = {a,b}; }
	template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
	template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
	template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}
 
using namespace input;
 
namespace output {
	void pr(int x) { cout << x; }
	void pr(long x) { cout << x; }
	void pr(ll x) { cout << x; }
	void pr(unsigned x) { cout << x; }
	void pr(unsigned long x) { cout << x; }
	void pr(unsigned long long x) { cout << x; }
	void pr(float x) { cout << x; }
	void pr(double x) { cout << x; }
	void pr(ld x) { cout << x; }
	void pr(char x) { cout << x; }
	void pr(const char* x) { cout << x; }
	void pr(const string& x) { cout << x; }
	void pr(bool x) { pr(x ? "true" : "false"); }
	template<class T> void pr(const complex<T>& x) { cout << x; }
	
	template<class T1, class T2> void pr(const pair<T1,T2>& x);
	template<class T> void pr(const T& x);
	
	template<class T, class... Ts> void pr(const T& t, const Ts&... ts) { 
		pr(t); pr(ts...); 
	}
	template<class T1, class T2> void pr(const pair<T1,T2>& x) { 
		pr("{",x.f,", ",x.s,"}"); 
	}
	template<class T> void pr(const T& x) { 
		pr("{"); // const iterator needed for vector<bool>
		bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; 
		pr("}");
	}
	
	void ps() { pr("\n"); } // print w/ spaces
	template<class T, class... Ts> void ps(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(" "); ps(ts...); 
	}
	
	void pc() { pr("]\n"); } // debug w/ commas
	template<class T, class... Ts> void pc(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(", "); pc(ts...); 
	}
	#define dbg(x...) pr("[",#x,"] = ["), pc(x);
}
 
using namespace output;
 
namespace io {
	void setIn(string s) { freopen(s.c_str(),"r",stdin); }
	void setOut(string s) { freopen(s.c_str(),"w",stdout); }
	void setIO(string s = "") {
		ios_base::sync_with_stdio(0); cin.tie(0); // fast I/O
		// cin.exceptions(cin.failbit); 
		// throws exception when do smth illegal
		// ex. try to read letter into int
		if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
	}
}
 
using namespace io;
 
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 
 
 
/**
 * Description: 1D range update and query. Set SZ to a power of 2.
 * Source: USACO Counting Haybales
 * Verification: SPOJ Horrible
 */
const ll ID = -100000000000000000;
 
template<class T, int SZ> struct LazySeg { 
	T sum[2*SZ], lazy[2*SZ]; 
	LazySeg() { F0R(i,2*SZ) sum[i] = lazy[i] = 0; }
	void push(int ind, int L, int R) { /// modify values for current node
		if (L != R) F0R(i,2) lazy[2*ind+i] += lazy[ind]; /// prop to children
		sum[ind] += lazy[ind]; lazy[ind] = 0; 
	} // recalc values for current node
	void pull(int ind) { sum[ind] = max(sum[2*ind], sum[2*ind+1]); }
	void build() { ROF(i,1,SZ) pull(i); }
	void upd(int lo,int hi,T inc,int ind=1,int L=0, int R=SZ-1) {
		push(ind,L,R); if (hi < L || R < lo) return;
		if (lo <= L && R <= hi) { 
			lazy[ind] = inc; push(ind,L,R); return; }
		int M = (L+R)/2;
		upd(lo,hi,inc,2*ind,L,M); upd(lo,hi,inc,2*ind+1,M+1,R); 
		pull(ind);
	}
	T qsum(int lo, int hi, int ind=1, int L=0, int R = SZ-1) {
		push(ind,L,R); if (lo > R || L > hi) return ID;
		if (lo <= L && R <= hi) return sum[ind];
		int M = (L+R)/2; 
		return max(qsum(lo,hi,2*ind,L,M), qsum(lo,hi,2*ind+1,M+1,R));
	}
};
 
 
ll ans;
vector<pair<int, ll>> be[200005];
vector<pair<int, ll>> en[200005];
LazySeg<ll, 262144> lseg;
 
int main() {
	setIO();
	
	int N, M;
	cin >> N >> M;
	for(int i = 1; i <= M; i++){
		int l, r;
		ll a;
		cin >> l >> r >> a;
		be[l].pb(mp(r, a));
		en[r].pb(mp(l, a));
	}
	for(int i = 1; i <= N+3; i++){
		lseg.upd(i, i, ID);
	}
	for(int i = 0; i <= N; i++){
		ll val = lseg.qsum(0, i);
		//ps("i, val", i, val);
		//ps(lseg.qsum(0, 0));
		ans = max(val, ans);
		if(i > 0) lseg.upd(i, i, -ID);
		lseg.upd(i, i, val);
		//ps("UPD", i, i, val);
		for(auto u: en[i]){
			lseg.upd(0, u.f-1, -(u.s));
			//ps("UPD", u.f, i, -(u.s));
		}
		for(auto u: be[i+1]){
			lseg.upd(0, i, u.s);
			//ps("UPD", 0, i, (u.s));
		}
	}
	ps(ans);
	// you should actually read the stuff at the bottom
}
 
/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?)
	* do smth instead of nothing and stay organized
	* WRITE STUFF DOWN
*/

Measured memory_bytes: 30336