func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     bool a[m + 1];     memset(a, 0, sizeof(a));     for (int i = 1; i <= n; i++) {       int l, r;       cin >> l >> r;       for (int j = l; j <= r; j++) a[j] = 1;     }     vector<int> v;     int res = 0;     for (int i = 1; i <= m; i++) {       if (a[i] == 0) {         res++;         v.push_back(i);       }     }     cout << res << endl;     for (int i = 0; i < v.size(); i++) cout << v[i] <<    ;   }   