#include <cassert>
#include "limits.h"
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
#include <random>
#include <memory>
#include <utility>
 
#define rep(i, a, b) for (long long (i) = (a); i < (b); i++)
#define all(i) i.begin(), i.end()
#define debug(i) std::cerr << "debug " <<"LINE:"<<__LINE__<<"  "<< #i <<":"<< i << std::endl

 
template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}
 
template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (int i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}
 
template<typename T1,typename T2>
inline bool chmax(T1& a,T2 b){return a<b && (a=b,true);}
 
template<typename T1,typename T2>
inline bool chmin(T1& a,T2 b){return a>b && (a=b,true);}
 
long long pow_mod(long long a, long long b, long long mod=-1) {
  if ((a == 0)||(mod!=-1&&a%mod==0)) {
    return 0;
  }
 
  long long x = 1;
 
  while (b > 0) {
    if (b & 1) {
      x = (mod!=-1)?(x * a) % mod:x*a;
    }
    a = (mod!=-1)?(a * a) % mod:a*a;
    b >>= 1;
  }
  return x;
}
 
// const long long MOD = 998244353;
const long long MOD = 1e9 + 7;

using ll = long long;
using P = std::pair<long long,long long>;

//非再帰抽象セグ木 0-indexed 単位元はiで指定
template <class T>
class SegmentTree {
 private:
  long long n;
  T init;
  std::vector<T> dat;
  std::function<T(T, T)> fn;

 public:
  SegmentTree(long long i, T para, std::function<T(T, T)> fun)
      : init(para), fn(fun) {
    n = 1;
    while (n < i) {
      n *= 2;
    }
    dat = std::vector<T>(2 * n - 1, init);
  }

  SegmentTree(const std::vector<T>& seq,T para,std::function<T(T,T)> fun)
      : init(para),fn(fun){
    n=1;
    while(n<seq.size())n<<=1;
    dat=std::vector<T>(2*n-1,init);
    for(long long i=0;i<seq.size();i++)dat[i+n-1]=seq[i];
    for(long long i=n-2;i>=0;i--)dat[i]=fn(dat[i*2+1],dat[i*2+2]);
  }

  // k番目(0-indexed)を値aで更新,dest=trueのときは更新前を破壊して初期化する
  void update(long long k, T a, bool dest) {
    assert(0<=k&&k<n);
    k += n - 1;
    if (dest) dat[k] = a;
    else dat[k] = fn(dat[k], a);

    while (k > 0) {
      k = (k - 1) / 2;
      dat[k] = fn(dat[k * 2 + 1], dat[k * 2 + 2]);
    }
  }

  //[a,b)の値を返す
  T query(long long a, long long b){
    assert(0<=a&&b<=n);
    T val=init;

    long long l=a+n-1,r=b+n-1;
    for(;l<r;l=(l>>1),r=(r>>1)){
      if(!(r&1)){
        r--;
        val=fn(val,dat[r]);
      }
      if(!(l&1)){
        val=fn(val,dat[l]);
        l++;
      }
    }

    return val;
  }
};

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

  ll n;
  std::cin>>n;

  std::vector<SegmentTree<P>> seg(2,SegmentTree<P>(n,{MOD,-1},[](P a,P b){return (a.first<b.first)?a:b;}));

  rep(i,0,n){
    ll a;
    std::cin>>a;
    seg[i%2].update(i,{a,i},true);
  }

  struct sec{
    ll min,l,r;
  };

  auto comp=[](sec a,sec b){return a.min>b.min;};

  std::priority_queue<sec,std::vector<sec>,decltype(comp)> que{comp};

  std::vector<ll> ans;

  que.push({seg[0].query(0,n).first,0,n});

  while(!que.empty()){
    sec e=que.top();que.pop();

    P left=seg[e.l%2].query(e.l,e.r);
    ans.push_back(left.first);
    P right=seg[(e.l+1)%2].query(left.second+1,e.r);
    ans.push_back(right.first);

    if(left.second-e.l>0)que.push({seg[e.l%2].query(e.l,left.second).first,e.l,left.second});
    if(right.second-left.second>1)que.push({seg[(left.second+1)%2].query(left.second+1,right.second).first,left.second+1,right.second});
    if(e.r-right.second>1)que.push({seg[(right.second+1)%2].query(right.second+1,e.r).first,right.second+1,e.r});
  }

  for(ll e:ans)std::cout<<e<<" ";
  std::cout<<"\n";

  return 0;
}




Measured memory_bytes: 24832