func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     vector<int> starts(m), ends(m), results;     for (int i = 0; i < n; i++) {       int l, r;       cin >> l >> r;       starts[l - 1]++;       ends[r - 1]++;     }     int open = 0;     for (int i = 0; i < m; i++) {       open += starts[i];       if (open == 0) results.push_back(i + 1);       open -= ends[i];     }     std::cout << results.size() << std::endl;     for (auto p : results) cout << p <<    ;     cout << endl;     return 0;   }   