// Balkan Olympiad in Informatics 2011 Day 1 Problem 3
// Medians
// https://oj.uz/problem/view/balkan11_medians
#include <bits/stdc++.h>
using namespace std;
int N;
vector<int> A, B;
bool seen[200001];
int minIndex, maxIndex;
int findMax() {
while (maxIndex >= 1 && seen[maxIndex]) {
maxIndex--;
}
seen[maxIndex] = true;
return maxIndex;
}
int findMin() {
while (minIndex <= N && seen[minIndex]) {
minIndex++;
}
seen[minIndex] = true;
return minIndex;
}
int main() {
cin >> N;
B.resize(N+1);
for (int i = 1; i <= N; i++) {
cin >> B[i];
}
A.push_back(B[1]);
seen[B[1]] = true;
minIndex = 1;
maxIndex = 2*N-1;
for (int i = 2; i <= N; i++) {
if (B[i] == B[i-1]) {
A.push_back(findMax());
B.push_back(findMin());
}
if (B[i] > B[i-1]) {
A.push_back(findMax());
if (seen[B[i]]) {
A.push_back(findMax());
}
else {
A.push_back(B[i]);
seen[B[i]] = true;
}
}
if (B[i] < B[i-1]) {
A.push_back(findMin());
if (seen[B[i]]) {
A.push_back(findMin());
}
else {
A.push_back(B[i]);
seen[B[i]] = true;
}
}
}
for (auto v: A) {
cout << v << " ";
} cout << "\n";
}
