#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> p(n);
    map<int, pair<int, int>> mp;
    for (auto &e : p) {
        cin >> e;
        mp[e] = {-1, -1};
    }
    for (int i = 0; i < n; i++) {
        if (i - 1 >= 0) {
            mp[p[i]].first = p[i - 1];
        }
        if (i + 1 < n) {
            mp[p[i]].second = p[i + 1];
        }
    }
    vector<int> ans;
    for (int i = 1; i <= n; i++) {
        const auto [prv, nxt] = mp[i];
        if (nxt == -1) {
            continue;
        }
        ans.push_back(i);
        ans.push_back(nxt);
        auto &[nprv, nnxt] = mp[nxt];
        if (prv != -1) {
            mp[prv].second = nnxt;
        }
        if (nnxt != -1) {
            mp[nnxt].second = prv;
        }
        nprv = -1;
        nnxt = -1;
    }
    for (int i = 0; i < ans.size(); i++) {
        cout << ans[i] << " \n"[i == n - 1];
    }
    return 0;
}