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

#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define all(x) (x).begin(),(x).end()
#define bit(n) (1LL<<(n))
#define sz(x) ((int)(x).size())
#define TEN(n) ((ll)(1e##n))
#define fst first
#define snd second

string DBG_DLM(int &i){return(i++==0?"":", ");}
#define DBG_B(exp){int i=0;os<<"{";{exp;}os<<"}";return os;}
template<class T>ostream&operator<<(ostream&os,vector<T>v);
template<class T>ostream&operator<<(ostream&os,set<T>v);
template<class T>ostream&operator<<(ostream&os,queue<T>q);
template<class T>ostream&operator<<(ostream&os,priority_queue<T>q);
template<class T,class K>ostream&operator<<(ostream&os,pair<T,K>p);
template<class T,class K>ostream&operator<<(ostream&os,map<T,K>mp);
template<class T,class K>ostream&operator<<(ostream&os,unordered_map<T,K>mp);
template<int I,class TPL>void DBG(ostream&os,TPL t){}
template<int I,class TPL,class H,class...Ts>void DBG(ostream&os,TPL t){os<<(I==0?"":", ")<<get<I>(t);DBG<I+1,TPL,Ts...>(os,t);}
template<class T,class K>void DBG(ostream&os,pair<T,K>p,string delim){os<<"("<<p.first<<delim<<p.second<<")";}
template<class...Ts>ostream&operator<<(ostream&os,tuple<Ts...>t){os<<"(";DBG<0,tuple<Ts...>,Ts...>(os,t);os<<")";return os;}
template<class T,class K>ostream&operator<<(ostream&os,pair<T,K>p){DBG(os,p,", ");return os;}
template<class T>ostream&operator<<(ostream&os,vector<T>v){DBG_B(forr(t,v){os<<DBG_DLM(i)<<t;});}
template<class T>ostream&operator<<(ostream&os,set<T>s){DBG_B(forr(t,s){os<<DBG_DLM(i)<<t;});}
template<class T>ostream&operator<<(ostream&os,queue<T>q){DBG_B(for(;q.size();q.pop()){os<<DBG_DLM(i)<<q.front();});}
template<class T>ostream&operator<<(ostream&os,priority_queue<T>q){DBG_B(for(;q.size();q.pop()){os<<DBG_DLM(i)<<q.top();});}
template<class T,class K>ostream&operator<<(ostream&os,map<T,K>m){DBG_B(forr(p,m){os<<DBG_DLM(i);DBG(os,p,"->");});}
template<class T,class K>ostream&operator<<(ostream&os,unordered_map<T,K>m){DBG_B(forr(p,m){os<<DBG_DLM(i);DBG(os,p,"->");});}
#define DBG_OVERLOAD(_1,_2,_3,_4,_5,_6,macro_name,...)macro_name
#define DBG_LINE(){char s[99];sprintf(s,"line:%3d | ",__LINE__);cerr<<s;}
#define DBG_OUTPUT(v){cerr<<(#v)<<"="<<(v);}
#define DBG1(v,...){DBG_OUTPUT(v);}
#define DBG2(v,...){DBG_OUTPUT(v);cerr<<", ";DBG1(__VA_ARGS__);}
#define DBG3(v,...){DBG_OUTPUT(v);cerr<<", ";DBG2(__VA_ARGS__);}
#define DBG4(v,...){DBG_OUTPUT(v);cerr<<", ";DBG3(__VA_ARGS__);}
#define DBG5(v,...){DBG_OUTPUT(v);cerr<<", ";DBG4(__VA_ARGS__);}
#define DBG6(v,...){DBG_OUTPUT(v);cerr<<", ";DBG5(__VA_ARGS__);}
#define DEBUG0(){DBG_LINE();cerr<<endl;}
#ifdef LOCAL
#define out(...){DBG_LINE();DBG_OVERLOAD(__VA_ARGS__,DBG6,DBG5,DBG4,DBG3,DBG2,DBG1)(__VA_ARGS__);cerr<<endl;}
#else
#define out(...)
#endif

using ll=long long;
using pii=pair<int,int>;using pll=pair<ll,ll>;using pil=pair<int,ll>;using pli=pair<ll,int>;
using vs=vector<string>;using vvs=vector<vs>;using vvvs=vector<vvs>;
using vb=vector<bool>;using vvb=vector<vb>;using vvvb=vector<vvb>;
using vi=vector<int>;using vvi=vector<vi>;using vvvi=vector<vvi>;
using vl=vector<ll>;using vvl=vector<vl>;using vvvl=vector<vvl>;
using vd=vector<double>;using vvd=vector<vd>;using vvvd=vector<vvd>;
using vpii=vector<pii>;using vvpii=vector<vpii>;using vvvpii=vector<vvpii>;
template<class A,class B>bool amax(A&a,const B&b){return b>a?a=b,1:0;}
template<class A,class B>bool amin(A&a,const B&b){return b<a?a=b,1:0;}
ll ri(){ll l;cin>>l;return l;} string rs(){string s;cin>>s;return s;}


template<class V, class Merge> struct SegmentTree {
  const int n;
  const V unit_value;
  vector<V> val;

  SegmentTree(int _n) : n(1 << (33-__builtin_clz(_n-1))), unit_value(Merge::unit()), val(n, unit_value) {}

  V get(int i) const { return val[i + n / 2]; }
  void set(int i, const V &v) { val[i + n / 2] = v; }

  void build() {
    for (int i = n / 2 - 1; i > 0; i--) val[i] = Merge::merge(val[i * 2 + 0], val[i * 2 + 1]);
  }

  void update(int i, const V &v) {
    i += n / 2;
    val[i] = v;
    while (i > 1) {
      i >>= 1;
      val[i] = Merge::merge(val[i * 2 + 0], val[i * 2 + 1]);
    }
  }

  V query(int l, int r) const {
    l = max(0, min(n / 2, l)) + n / 2;
    r = max(0, min(n / 2, r)) + n / 2;
    V ret = unit_value;
    for (; l < r; l >>= 1, r >>= 1) {
      if (l & 1) ret = Merge::merge(ret, val[l++]);
      if (r & 1) ret = Merge::merge(ret, val[--r]);
    }
    return ret;
  }
};
template <class V> struct MergeRangeMinQ {
  static V merge(const V &l, const V &r) { return l < r ? l : r; }
  static V unit() { return numeric_limits<V>::max(); }
};
template<class V> using SegTreeMin = SegmentTree<V, MergeRangeMinQ<V>>;

void Main() {
  int n = ri();
  vector<int> A(n);
  rep(i, n) A[i] = ri()-1;

  vi R(n);
  rep(i, n) R[A[i]] = i;

  SegTreeMin<int> segO(n);
  SegTreeMin<int> segE(n);

  rep(i, n) {
    (i % 2 ? segO : segE).set(i, A[i]);
  }

  segO.build();
  segE.build();

  priority_queue<pair<int, pii>, vector<pair<int, pii>>, greater<pair<int, pii>>> q;
  q.push({0, {0, n}});

  vi ans;

  while (!q.empty()) {
    int lef = q.top().snd.fst;
    int rig = q.top().snd.snd;
    q.pop();

    if (lef == rig) continue;

    auto &segA = lef % 2 ? segO : segE;
    auto &segB = lef % 2 ? segE : segO;

    int mi1 = segA.query(lef, rig);
    int p1 = R[mi1];
    int mi2 = segB.query(p1, rig);
    int p2 = R[mi2];

    ans.emplace_back(mi1+1);
    ans.emplace_back(mi2+1);

    q.push({segA.query(lef, p1), {lef, p1}});
    q.push({segB.query(p1+1, p2), {p1+1, p2}});
    q.push({segA.query(p2+1, rig), {p2+1, rig}});
  }
  rep(i, n) {
    cout << ans[i];
    if (i + 1 < n) cout << ' ';
    else cout << endl;
  }
}

signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  Main();
  return 0;
}

Measured memory_bytes: 11440