#include <bits/stdc++.h>   using namespace std;   using ll = long long;   using pii = pair<int, int>;   using pll = pair<ll, ll>;   using pdd = pair<double, double>;   using vi = vector<int>;   using vii = vector<pii>;   using vs = vector<string>;   const double PI = acos(-1.0);   const double EPS = 1e-14;   const int MOD = 1e9 + 7;   const int INF = 1e9;   const ll INFLL = 4e18;   const int MAX = 1e5;   int n, m;   set<int> hv, ans;   void read() {     cin >> n >> m;     for (int i = 0; i < (int)n; i++) {       int t;       cin >> t;       hv.insert(t);     }   }   void solve() {     for (int i = (int)1; i <= (int)1e9; i++) {       if (i > m) break;       if (!(hv.find(i) != hv.end())) {         ans.insert(i);         m -= i;       }     }     cout << (int)ans.size() <<   n ;     for (int t : ans) {       cout << t <<    ;     }   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int TC = 1;     while (TC--) {       read();       solve();     }   }   