#include <iostream>
#include <map>
#include <set>
#include <vector>

int main() {
    using namespace std;
    int n;
    cin >> n;
    map<int, int> m;
    set<pair<int, int>> s;
    vector<int> ans;
    for (int p, i = 0; i < n; ++i)
        cin >> p, s.emplace(i, p), m[p] = i;
    for (int j = 1; j <= n; ++j)
        if (m.at(j) < n - 1) {
            ans.push_back(j);
            s.erase({m.at(j), j});
            auto it = s.lower_bound({m.at(j) + 1, 0});
            auto [_, u] = *it;
            ans.push_back(u);
            m.at(u) = n;
            s.erase(it);
        }
    for (bool first = true; const auto& i : ans) {
        if (first)
            first = false;
        else
            cout << ' ';
        cout << i;
    }
    cout << '\n';
}