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

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
//typedef vector<vector<ll>> Graph;

const ll mod = 1e9 + 7;
//const ll mod = 998244353;

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define spa << " " <<
#define fi first
#define se second

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){
os << "(" << v.first << ", " << v.second << ")"; return os;
}
template<class T> ostream& operator << (ostream& os, const vector<T> v){
for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << " ";} os << v[i];} return os;
}
template<class T> ostream& operator << (ostream& os, const vector<vector<T>> v){
for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << endl;} os << v[i];} return os;
}

template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<endl;}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<endl;};

const ll INF = (1ll<<60);

template< typename Monoid >
struct SegmentTree {
  using F = function< Monoid(Monoid, Monoid) >;

  int sz;
  vector< Monoid > seg;

  const F f;
  const Monoid M1;

  // n: 要素数，F: モノイド間の演算，M1: 演算の単位元
  // F は無名関数で渡す
  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    sz = 1;
    while(sz < n) sz <<= 1;
    seg.assign(2 * sz, M1);
  }

  // k番目の要素にxを代入
  void set(int k, const Monoid &x) {
    seg[k + sz] = x;
  }

  // 構築
  void build() {
    for(int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  // k番目の値をxに変更
  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while(k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  // 区間[a, b)に関して演算して結果を返す
  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) L = f(L, seg[a++]);
      if(b & 1) R = f(seg[--b], R);
    }
    return f(L, R);
  }

  // k番目の値を返す(set[k]でアクセス)
  Monoid operator[](const int &k) const {
    return seg[k + sz];
  }


  template< typename C >
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while(a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if(check(nxt)) a = 2 * a + type;
      else M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }


  template< typename C >
  //[a, x)がcheckを満たす最初の要素位置xを返す
  // ↑嘘かも．[a, x]が正しい
  // 存在しない場合は-1を返すことに注意
  // Cには判定関数を入れる
  int find_first(int a, const C &check) {
    Monoid L = M1;
    if(a <= 0) {
      if(check(f(L, seg[1]))) return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) {
        Monoid nxt = f(L, seg[a]);
        if(check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }

  //[x, b)がcheckを満たす最後の要素位置xを返す
  template< typename C >
  int find_last(int b, const C &check) {
    Monoid R = M1;
    if(b >= sz) {
      if(check(f(seg[1], R))) return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for(b += sz; a < b; a >>= 1, b >>= 1) {
      if(b & 1) {
        Monoid nxt = f(seg[--b], R);
        if(check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};

struct dat{
    ll fi, se, pos_fi, pos_se, l, r;
    dat(ll fi, ll se, ll pos_fi, ll pos_se, ll l , ll r): fi(fi), se(se), pos_fi(pos_fi), pos_se(pos_se), l(l), r(r) {};
    bool operator>(const dat &right) const{
        return fi > right.fi;
    }
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll N;
    cin >> N;
    vector<ll> p(N);
    REP(i, N) cin >> p[i];

    auto f = [](pll a, pll b){
        return min(a, b);
    };
    pll e = {INF, -1};
    vector<SegmentTree<pll>> seg(2, SegmentTree<pll>(N, f, e));
    REP(i, N){
        seg[i%2].set(i, {p[i], i});
    }
    REP(i, 2) seg[i].build();

    priority_queue<dat, vector<dat>, greater<dat>> pq;

    auto make_dat = [&](ll l, ll r){
        auto [L, ldx] = seg[l%2].query(l, r);
        auto [R, rdx] = seg[(l+1)%2].query(ldx, r);  
        dat tmp(L, R, ldx, rdx, l, r);
        return tmp;
    };

    auto q = make_dat(0, N);
    pq.push(q);

    vector<pll> res;
    while(!pq.empty()){
        auto q = pq.top();pq.pop();
        res.emplace_back(q.fi, q.se);
        if(q.l<q.pos_fi){
            auto tmp = make_dat(q.l, q.pos_fi);
            pq.push(tmp);
        }
        if(q.pos_fi+1<q.pos_se){
            auto tmp = make_dat(q.pos_fi+1, q.pos_se);
            pq.push(tmp);
        }
        if(q.pos_se+1<q.r){
            auto tmp = make_dat(q.pos_se+1, q.r);
            pq.push(tmp);
        }
    }
    
    for(auto p: res){
        cout << p.first spa p.second << " ";
    }
    cout << endl;

    return 0;
}

Measured memory_bytes: 29328