#define _CRT_SECURE_NO_WARNINGS
#define debug(l) cerr<<" smorti hyuniy : "<<#l<<' '<<l<<'\n';
#include "bits/stdc++.h"
using namespace std;
#define all(a) a.begin(), a.end()
typedef long long ll;
typedef long double ld;
const ll MAXN = 72;
ll dp[MAXN][MAXN][MAXN]={};
signed main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    ll n, m;
    cin >> n >> m;
    struct Point {
        ll x, type, val;
    };
    map<ll, ll> inser;
    vector<Point> line;
    for (ll i = 0; i < m; i++) {
        ll l, r, val;
        cin >> l >> r >> val;
        inser[l] = max(inser[l], val);
        inser[r] = max(inser[r], val);
        line.push_back({ l,+1,val });
        line.push_back({ r,-1,val });
    }
    auto cmp = [&](Point& a, Point& b) {
        return (a.x < b.x || (a.x == b.x && a.type > b.type));
    };
    sort(all(line), cmp);
    ll last_x = -1;
    ll ans = 0;
    multiset<ll> cur;
    ans += inser[1];
    map<ll, ll> used;
    for (Point& x : line) {
        if (last_x != -1) {
            if (used[x.x])continue;
            auto it = cur.end();
            it--;
            ans += max(inser[x.x], *it);
            ans += (x.x - last_x - 1) * (*it);
            used[x.x] = 1;
        }
        last_x = x.x;
        if (x.type == -1) {
            cur.erase(cur.find(x.val));
        }
        else {
            cur.insert(x.val);
        }
    }
    cout << ans << '\n';
}