func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e3 + 5;   int main() {     int num, r;     cin >> num >> r;     vector<pair<int, int>> arr(num + 1);     vector<bool> visited(r + 2, 0);     for (int i = 1; i <= num; ++i) {       cin >> arr[i].first >> arr[i].second;       for (int j = arr[i].first; j <= arr[i].second; ++j) {         visited[j] = 1;       }     }     long long ans = 0;     for (int k = 1; k <= r; ++k) {       if (visited[k] == 0) ans++;     }     cout << ans <<   n ;     for (int k = 1; k <= r; ++k) {       if (visited[k] == 0) cout << k <<    ;     }   }   