#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pii;
typedef pair<double,double> pdd;
#define MEM(a, b) memset(a, (b), sizeof(a))
#define SZ(i) ll(i.size())
#define FOR(i, j, k, in) for (ll i=j ; i<k ; i+=in)
#define RFOR(i, j, k, in) for (ll i=j ; i>=k ; i-=in)
#define REP(i, j) FOR(i, 0, j, 1)
#define REP1(i,j) FOR(i, 1, j+1, 1)
#define RREP(i, j) RFOR(i, j, 0, 1)
#define ALL(_a) _a.begin(),_a.end()
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define X first
#define Y second
#ifdef tmd
#define debug(...) do{\
    fprintf(stderr,"%s - %d (%s) = ",__PRETTY_FUNCTION__,__LINE__,#__VA_ARGS__);\
    _do(__VA_ARGS__);\
}while(0)
template<typename T>void _do(T &&_x){cerr<<_x<<endl;}
template<typename T,typename ...S> void _do(T &&_x,S &&..._t){cerr<<_x<<" ,";_do(_t...);}
template<typename _a,typename _b> ostream& operator << (ostream &_s,const pair<_a,_b> &_p){return _s<<"("<<_p.X<<","<<_p.Y<<")";}
template<typename It> ostream& _OUTC(ostream &_s,It _ita,It _itb)
{
    _s<<"{";
    for(It _it=_ita;_it!=_itb;_it++)
    {
        _s<<(_it==_ita?"":",")<<*_it;
    }
    _s<<"}";
    return _s;
}
template<typename _a> ostream &operator << (ostream &_s,vector<_a> &_c){return _OUTC(_s,ALL(_c));}
template<typename _a> ostream &operator << (ostream &_s,set<_a> &_c){return _OUTC(_s,ALL(_c));}
template<typename _a,typename _b> ostream &operator << (ostream &_s,map<_a,_b> &_c){return _OUTC(_s,ALL(_c));}
template<typename _t> void pary(_t _a,_t _b){_OUTC(cerr,_a,_b);cerr<<endl;}
#define IOS()
#else
#define debug(...)
#define pary(...)
#define endl '\n'
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0)
#endif

template<class T> inline bool cmax(T &a, const T &b) { return b > a ? a = b, true : false; }
template<class T> inline bool cmin(T &a, const T &b) { return b < a ? a = b, true : false; }
template<class T> using MaxHeap = priority_queue<T>;
template<class T> using MinHeap = priority_queue<T, vector<T>, greater<T>>;

const ll MOD=1000000007;
const ll INF=0x3f3f3f3f3f3f3f3f;
const ll MAXN=2e5+5;
const ll MAXLG=__lg(MAXN)+2;


namespace seg {
    struct node {
        ll l,r;
        node *lc,*rc;
        ll data,tag;
        void push() {
            if (lc && rc) {
                lc->tag += tag;
                rc->tag += tag;
            }
            data += tag;
            tag = 0;
        }
        void pull() {
            if (lc && rc) {
                data = max(lc->data+lc->tag,rc->data+rc->tag);
            }
        }
    };
    node *root;
    node *build (ll l,ll r) {
        if (l == r - 1) {
            return new node {l,r,NULL,NULL,0,0};
        }
        ll mid = l + r >> 1;
        return new node {l,r,build(l,mid),build(mid,r),0,0};
    }

    ll query(ll l,ll r,node *nd) {
        nd->push();
        if (l == nd->l && r == nd->r) {
            return nd->data;
        }
        ll mid = nd->l + nd->r >> 1;
        if (l >= mid) {
            return query(l,r,nd->rc);
        } else if (r <= mid) {
            return query(l,r,nd->lc);
        } else {
            return max(query(l,mid,nd->lc),query(mid,r,nd->rc));
        }
    }

    void add(ll l,ll r,node *nd,ll val) {
        nd->push();
        if (l == nd->l && r == nd->r) {
            nd->tag += val;
            return;
        }
        ll mid = nd->l + nd->r >> 1;
        if (l >= mid) {
            add(l,r,nd->rc,val);
        } else if (r <= mid) {
            add(l,r,nd->lc,val);
        } else {
            add(l,mid,nd->lc,val);
            add(mid,r,nd->rc,val);
        }
        nd->pull();
    }
}
ll n,m;

vector<pii> query[MAXN];
/********** Good Luck :) **********/
int main()
{
    IOS();
    cin >> n >> m;
    seg::root = seg::build(0,n+1);
    REP (i,m) {
        ll l,r,val;
        cin >> l >> r >> val;
        query[l].push_back({l,val});
        query[r+1].push_back({l,-val});
    }

    ll ans = 0;
    REP1 (i,n) {
        for (auto p : query[i]) {
            seg::add(0,p.X,seg::root,p.Y);
        }
        ll cur = seg::query(0,i,seg::root);
        seg::add(i,i+1,seg::root,cur);
        ans = max(ans,cur);
    }

    cout << ans << endl;
    return 0;
}
//DP

Measured memory_bytes: 40448