#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
#include <numeric>
#include <map>
#include <sstream>
#include <cstring>
#include <stack>
#include <climits>
using namespace std;
const long long INF = 1e9;
int n;
int b[2005];
vector<int> a;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("cowtip.in", "r", stdin);
// freopen("cowtip.out", "w", stdout);
int n; cin >> n;
bool used[2005];
memset(used, false, sizeof(used));
for (int i = 1; i <= n; i++) {
cin >> b[i];
}
int m = 2*n - 1;
int num = 1;
for (int i = 1; i <= n; i++) {
bool check = false;
int higher = 0, lower = 0;
int elements = 2 * i - 1;
for(int x : a) {
if (x > b[i]) {
higher++;
} else if (x < b[i]) {
lower++;
}
}
if(!used[b[i]]) {
a.push_back(b[i]);
used[b[i]] = true;
}
while((int)a.size() != elements) {
if(lower > higher) {
while(m > 0 && used[m]) {
m--;
}
if (m <= 0) break;
a.push_back(m);
used[m] = true;
higher++;
} else if (lower < higher) {
while(num <= m && used[num]) {
num++;
}
if (num > 2*n - 1) break;
a.push_back(num);
used[num] = true;
lower++;
} else if (lower == higher) {
while(m > 0 && used[m]) {
m--;
}
if (m <= 0) break;
a.push_back(m);
used[m] = true;
higher++;
while(num <= m && used[num]) {
num++;
}
if (num > 2*n - 1) break;
a.push_back(num);
used[num] = true;
lower++;
}
}
}
for (auto v : a) {
cout << v << " ";
}
cout << "\n";
return 0;
}
