/*
         --┬--  |     |  --┬--                |       |
           |    |\    |    |                  |       |
           |    | \   |    |     ----->       |       |
           |    |  \  |    |                  |       |
           |    |   \ |    |                  |       |
         --┴--  |    \|    |                  └----   └----

*/

#define pragma

#ifdef pragma
#pragma GCC optimize("Ofast")
#pragma GCC optimize("no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#endif // pragma

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

#define ll long long
#define all(x) begin(x),end(x)
#define pb push_back
#define x first
#define y second
#define INF 9223372036854775807ll
#define PI 3.14159265359d
#define INPUT "input.txt"
#define OUTPUT "output.txt"
#define sz size
#define rsz resize
#define int long long

using namespace std;

typedef vector<int> vi;
typedef vector<bool> vb;
typedef pair<int,int> pii;
typedef long double ld;
typedef vector<vi> matrix;

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    #ifdef _android
        freopen("input", "r", stdin);
        freopen("output", "w", stdout);
    #else
        //_android
    #endif
}

struct node {
    int val, df;
};

node t[10000000 * 8];

void push(int v) {
    t[v].val += t[v].df;
    t[v * 2 + 1].df += t[v].df;
    t[v * 2 + 2].df += t[v].df;
    t[v].df = 0;
}

void update(int v, int l, int r, int tl, int tr, int val) {
    //cerr << tl << " " << tr << " " << l << " " << r << endl;
    push(v);
    if(tl > r || tr < l) {
        return;
    }
    if(tl >= l && tr <= r) {
        t[v].df += val;
        push(v);
        return;
    }
    int tm = (tl + tr) >> 1;
    update(v * 2 + 1, l, r, tl, tm, val);
    update(v * 2 + 2, l, r, tm + 1, tr, val);
    t[v].val = max(t[v * 2 + 1].val, t[v * 2 + 2].val);
}

int getmax(int v, int l, int r, int tl, int tr) {
    push(v);
    if(tl > r || tr < l) {
        return -1;
    }
    if(tl >= l && tr <= r) {
        return t[v].val;
    }
    int tm = (tl + tr) >> 1;
    int x = getmax(v * 2 + 1, l, r, tl, tm);
    int y = getmax(v * 2 + 2, l, r, tm + 1, tr);
    return max(x, y);
}

signed main(){
    seriy();
    int n, m;
    cin >> n >> m;
    for(int i = 0; i < m; i++) {
        int l, r, val;
        cin >> l >> r >> val;
        l--, r--;
        update(0, l, r, 0, n - 1, val);
    }
    cout << getmax(0, 0, n - 1, 0, n - 1);
//    cout << endl;
//    for(auto i : t) cout << i.val << " ";
    return 0;
}