#include <bits/stdc++.h>
// #include <atcoder/all>
#include <iostream>
#include <math.h>

using namespace std;
// using namespace atcoder;
// using mint = modint998244353;
// using mint = modint1000000007;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using ll = long long;
template <class T> using max_heap = priority_queue<T>;
template <class T> using min_heap = priority_queue<T, vector<T>, greater<>>;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, f, n) for (int i = (int) f; i < (int)(n); i++)
#define repd(i, n, l) for (int i = (int) n; i >= (int) l; i--)

const ll inf = ll(1e9+7);


int n;

int main() {
    cin >> n;
    vector<int> p(n);
    rep(i, n) cin >> p[i];
    vector<int> idx(n+1);
    rep(i, n){
        idx[p[i]] = i;
    }
    vector<int> nxt(n);
    vector<int> pre(n);
    rep(i, n) {
        nxt[i] = i+1;
        pre[i] = i-1;
    }

    vector<int> ans;
    for (int i = 1; i <= n; i++){
        if (p[idx[i]] == -1) continue;
        if (idx[i] == n-1) continue;
        if (nxt[idx[i]] == n) continue;

        ans.push_back(i);
        ans.push_back(p[nxt[idx[i]]]);
        if (pre[idx[i]] >= 0) nxt[pre[idx[i]]] = min(nxt[nxt[idx[i]]], n);
        if (nxt[nxt[idx[i]]] < n) pre[nxt[nxt[idx[i]]]] = max(pre[idx[i]], -1);
        p[idx[i]] = -1;
        p[nxt[idx[i]]] = -1;
    }
    rep(i, n) {
        if (i == n-1) cout << ans[i] << endl;
        else cout << ans[i] << ' ';
    } 
    return 0;
}