func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m, i, j, first, end, count = 0;     cin >> n >> m;     vector<int> a(m + 1, 0);     for (i = 0; i < n; i++) {       cin >> first >> end;       for (j = first; j <= end; j++) a[j] = 1;     }     for (i = 1; i < m + 1; i++) {       if (a[i] == 0) count++;     }     cout << count << endl;     for (i = 1; i < m + 1; i++) {       if (a[i] == 0) cout << i <<    ;     }     return 0;   }   