#include <bits/stdc++.h> #define st first #define nd second #define pb push_back #define mp make_pair #define all(x) x.begin(), x.end() #define len(x) (int)x.size() #define fastio() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL) using namespace std; using ll = long long; using ull = unsigned long long; using ld = long double; mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); mt19937_64 rng64(chrono::high_resolution_clock::now().time_since_epoch().count()); inline int gen(int l, int r){return uniform_int_distribution<int>(l, r)(rng);} inline ll gen(ll l, ll r){return uniform_int_distribution<ll>(l, r)(rng64);} template<typename T, typename H> ostream& operator<<(ostream& os, const pair<T, H> &p){ return os << '(' << p.st << ", " << p.nd << ')'; } template<typename T> ostream& operator<<(ostream& os, const vector<T> &vec){ os << '{'; for(int i = 0; i < len(vec); i++){ if(i != 0) os << ", "; os << vec[i]; } os << '}'; return os; } const int N = 100'007; int n; int t[N]; bool blocked[N*2]; bool used[N*2]; void next_left(int &left){ while(used[left] || blocked[left]) left++; } void next_right(int &right){ while(used[right] || blocked[right]) right--; } void solve(){ cin >> n; for(int i = 0; i < n; i++) cin >> t[i]; cout << t[0] << ' '; used[t[0]] = true; int left = 1; int right = n*2 - 1; for(int i = 1; i < n; i++){ if(t[i] < t[i-1]){ cout << t[i] << ' '; used[t[i]] = true; next_left(left); cout << left << ' '; used[left] = true; left++; }else if(t[i] > t[i-1]){ cout << t[i] << ' '; used[t[i]] = true; next_right(right); cout << right << ' '; used[right] = true; right--; }else{ next_left(left); cout << left << ' '; used[left] = true; left++; next_right(right); cout << right << ' '; used[right] = true; right--; } } cout << '\n'; } int32_t main(){ fastio(); int tt = 1; // cin >> tt; while(tt--) solve(); return 0; }