#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long INF = (long long)1000000007 * 1000000007;
const long double eps = 1e-8;
const long double pi = acos(-1.0);
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
template <typename T>
struct SegmentTree {
  using F = function<T(T, T)>;
  int n;
  F f;
  T ti;
  vector<T> dat;
  SegmentTree() {}
  SegmentTree(F f, T ti) : f(f), ti(ti) {}
  void init(int n_) {
    n = 1;
    while (n < n_) n <<= 1;
    dat.assign(n << 1, ti);
  }
  void build(const vector<T> &v) {
    int n_ = v.size();
    init(n_);
    for (int i = 0; i < n_; i++) dat[n + i] = v[i];
    for (int i = n - 1; i; i--)
      dat[i] = f(dat[(i << 1) | 0], dat[(i << 1) | 1]);
  }
  void set_val(int k, T x) {
    dat[k += n] = x;
    while (k >>= 1) dat[k] = f(dat[(k << 1) | 0], dat[(k << 1) | 1]);
  }
  T query(int a, int b) {
    if (a >= b) return ti;
    T vl = ti, vr = ti;
    for (int l = a + n, r = b + n; l < r; l >>= 1, r >>= 1) {
      if (l & 1) vl = f(vl, dat[l++]);
      if (r & 1) vr = f(dat[--r], vr);
    }
    return f(vl, vr);
  }
  template <typename C>
  int find(int st, C &check, T &acc, int k, int l, int r) {
    if (l + 1 == r) {
      acc = f(acc, dat[k]);
      return check(acc) ? k - n : -1;
    }
    int m = (l + r) >> 1;
    if (m <= st) return find(st, check, acc, (k << 1) | 1, m, r);
    if (st <= l && !check(f(acc, dat[k]))) {
      acc = f(acc, dat[k]);
      return -1;
    }
    int vl = find(st, check, acc, (k << 1) | 0, l, m);
    if (~vl) return vl;
    return find(st, check, acc, (k << 1) | 1, m, r);
  }
  template <typename C>
  int find(int st, C &check) {
    T acc = ti;
    return find(st, check, acc, 1, 0, n);
  }
  T &operator[](int i) { return dat[i + n]; };
};
int n, m;
vector<pair<long long, int> > ls[100010];
void solve() {
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int l, r;
    long long c;
    cin >> l >> r >> c;
    l--;
    r--;
    ls[r].emplace_back(c, l);
  }
  SegmentTree<long long> seg([](long long a, long long b) { return min(a, b); },
                             INF);
  seg.init(n - 1);
  seg.set_val(0, 0);
  for (int i = 1; i < n; i++) {
    long long res = INF;
    for (pair<long long, int> p : ls[i]) {
      int l = p.second;
      long long c = p.first;
      res = min(res, seg.query(l, i) + c);
    }
    seg.set_val(i, res);
  }
  cout << seg[n - 1] << endl;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(50);
  solve();
}
