#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
#define int ll
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef RUS_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";


template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1>
inline istream & operator >> (istream &in, pair<T0, T1> &a) {
    return in >> a.first >> a.second;
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}


void smain();



signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
#ifdef RUS_HOME
    freopen("input", "r", stdin);
    clock_t start = clock();
#endif
    cout << setprecision(12) << fixed;
    smain();
#ifdef RUS_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

const int N=2e5+100,oo=1e18;
int t[4*N],pushing[4*N];
vpi gl[N],gr[N];

void push(int v){
    if(!pushing[v])
        return;
    t[v<<1]+=pushing[v];
    t[v<<1|1]+=pushing[v];
    pushing[v<<1]+=pushing[v];
    pushing[v<<1|1]+=pushing[v];
    pushing[v]=0;
}

void upd(int v,int tl, int tr, int l, int r, int val){
    if(l>r)
        return;
    if(tl==l&&r==tr){
        t[v]+=val;
        pushing[v]+=val;
        return;
    }
    push(v);
    int tm=tl+tr>>1;
    upd(v<<1,tl,tm,l,min(tm,r),val);
    upd(v<<1|1,tm+1,tr,max(tm+1,l),r,val);
    t[v]=max(t[v<<1],t[v<<1|1]);
}

int get(int v,int tl,int tr,int l,int r){
    if(l>r)
        return -oo;
    if(tl==l&&r==tr){
        return t[v];
    }
    push(v);
    int tm=tl+tr>>1;
    return max(get(v<<1,tl,tm,l,min(tm,r)),
            get(v<<1|1,tm+1,tr,max(tm+1,l),r));
}

void smain() {

    int n,m;
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int l,r,a;
        cin>>l>>r>>a;
        gl[l].push_back({r,a});
        gr[r].push_back({l,a});
    }

    int ans=0;
    for(int i=1;i<=n;i++){
        for(auto p:gl[i]){
            upd(1,0,n,0,i-1,p.second);
        }
        int cur=get(1,0,n,0,i-1);
        inmax(ans,cur);
        upd(1,0,n,i,i,cur);
        for(auto p:gr[i]){
            upd(1,0,n,0,p.first-1,-p.second);
        }
    }


    cout<<ans;



}


Measured memory_bytes: 33280