#include <bits/stdc++.h>   using namespace std;   vector<pair<int, int> > vec[2102100];   pair<int, int> tr[2102100];   int lz[2102100];   int id[2102100];   int l[2102100];   int r[2102200];   int b[2102100];   int path[2102100];   int st[2102100];   void build(int p, int l, int r) {     tr[p] = {0, -1};     lz[p] = 0;     if (l == r) {       return;     }     int mid = l + r >> 1;     build(p << 1, l, mid);     build(p << 1 | 1, mid + 1, r);   }   void pushup(int p) { tr[p] = max(tr[p << 1], tr[p << 1 | 1]); }   void pushdown(int p) {     if (lz[p]) {       lz[p << 1] = lz[p << 1 | 1] = lz[p];       lz[p] = 0;       tr[p << 1] = tr[p << 1 | 1] = tr[p];     }   }   pair<int, int> query(int p, int l, int r, int ll, int rr) {     if (ll <= l && rr >= r) {       return tr[p];     }     pushdown(p);     int mid = l + r >> 1;     pair<int, int> res = {0, -1};     if (ll <= mid) res = max(query(p << 1, l, mid, ll, rr), res);     if (rr > mid) res = max(query(p << 1 | 1, mid + 1, r, ll, rr), res);     return res;   }   void update(int p, int l, int r, int ll, int rr, pair<int, int> res) {     if (ll <= l && rr >= r) {       tr[p] = res;       lz[p] = 1;       return;     }     pushdown(p);     int mid = l + r >> 1;     if (ll <= mid) update(p << 1, l, mid, ll, rr, res);     if (rr > mid) update(p << 1 | 1, mid + 1, r, ll, rr, res);     pushup(p);   }   int main() {     int n, t;     cin >> n >> t;     for (int i = 1; i <= t; i++) {       cin >> id[i] >> l[i] >> r[i];       b[i * 2 - 1] = l[i];       b[i * 2] = r[i];     }     sort(b + 1, b + 1 + t * 2);     int len = unique(b + 1, b + 1 + t * 2) - b - 1;     build(1, 1, len);     for (int i = 1; i <= t; i++) {       l[i] = lower_bound(b + 1, b + 1 + len, l[i]) - b;       r[i] = lower_bound(b + 1, b + 1 + len, r[i]) - b;       vec[id[i]].push_back({l[i], r[i]});     }     for (int i = 1; i <= n; i++) {       pair<int, int> mx = {0, -1};       for (auto tt : vec[i]) {         mx = max(mx, query(1, 1, len, tt.first, tt.second));       }       mx.first++;       path[i] = mx.second;       mx.second = i;       for (auto tt : vec[i]) {         update(1, 1, len, tt.first, tt.second, mx);       }     }     pair<int, int> ans = query(1, 1, len, 1, len);     int u = ans.second;     int aa = n;     while (u != -1) {       st[u] = 1;       aa--;       u = path[u];     }     cout << aa << endl;     for (int i = 1; i <= n; i++) {       if (!st[i]) cout << i <<    ;     }   }   