#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
using namespace std;
using ll = long long;
using ld = long double;
using V = vector<int>;
using Vll = vector<ll>;
using Vld = vector<ld>;
using Vbo = vector<bool>;
using VV = vector<V>;
using VVll = vector<Vll>;
using VVld = vector<Vld>;
using VVbo = vector<Vbo>;
using VVV = vector<VV>;
using VVVll = vector<VVll>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using Pld = pair<ld, ld>;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define rep(i, n) rep2(i, 0, n)
#define drep(i, n) drep2(i, n, 0)
#define all(a) (a).begin(), (a).end()
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
template<typename T> inline int sz(T &x) { return x.size(); }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << p.first << ' ' << p.second; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline int fLog2(const int x) { assert(x > 0); return 31-__builtin_clz(x); } // floor(log2(x))
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); }
inline int cLog2(const int x) { assert(x > 0); return (x == 1) ? 0 : 32-__builtin_clz(x-1); } // ceil(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
void fail() { puts("-1"); exit(0); }
const int INF  = 1<<30;
const ll INFll = 1ll<<62;
const ld EPS   = 1e-10;
const ld PI    = acos(-1.0);
// const int MOD  = int(1e9)+7;
// const int MOD  = 998244353;


template<typename T>
struct SparseTable {
  vector<T> v;
  VV st;
  int op(const int a, const int b) {
    return (v[a] == v[b]) ? min(a, b) : ((v[a] < v[b]) ? a : b);
  } 
  void init(const vector<T> &_v) {
    v = _v;
    int n = v.size();
    st = {V(n)}; iota(all(st[0]), 0);
    for (int j = 0; n>>(j+1); ++j) {
      int m = n+1-(1<<(j+1));
      st.push_back(V(m));
      rep(i, m) st[j+1][i] = op(st[j][i], st[j][i+(1<<j)]);
    }
  }
  int index(const int l, const int r) { int d = fLog2(r-l); return op(st[d][l], st[d][r-(1<<d)]); }
  T query(const int l, const int r) { return v[index(l, r)]; }
};


SparseTable<int> rmq[2];


int main() {
  int n; cin >> n;
  V p(n); cin >> p;
  VV q(2, V(n, INF));
  rep(i, n) q[i%2][i] = p[i];
  rep(i, 2) rmq[i].init(q[i]);

  auto f = [&] (int l, int r) {
    int m = l % 2;
    int i = rmq[m].index(l, r);
    return p[i];
  };

  priority_queue<pair<int, P>> pq;
  pq.emplace(-f(0, n), P{0, n});
  V ans;

  while (!pq.empty()) {
    auto [_, lr] = pq.top(); pq.pop();
    auto [l, r] = lr;

    int m = l % 2;
    int i = rmq[m].index(l, r);
    int j = rmq[m^1].index(i, r);
    ans.push_back(p[i]);
    ans.push_back(p[j]);
    
    if (l < i)   pq.emplace(-f(l, i), P{l, i});
    if (i+1 < j) pq.emplace(-f(i+1, j), P{i+1, j});
    if (j+1 < r) pq.emplace(-f(j+1, r), P{j+1, r});
  }

  cout << ans << '\n';
  return 0;
}


Measured memory_bytes: 35388