#include <bits/stdc++.h>

using namespace std;

#define INF 100000000
#define YJ 1145141919
#define INF_INT_MAX 2147483647
#define INF_LL_MAX 9223372036854775807
#define EPS 1e-10
#define MOD 1000000007
#define Pi acos(-1)
#define LL long long
#define ULL unsigned long long
#define LD long double

#define int long long

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(a)  begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())

class Node {
public:
    Node(pair<LL, LL> v = unitValue) : value(v.first), index(v.second) {

    }

    Node operator + (const Node& monoid) const {
      if(value < monoid.value) {
        return Node(make_pair(value, index));
      } else {
        return monoid;
      }
    }

    static Node unit() {
        return Node(unitValue);
    }

    void setValue(LL l) {
        this->value = l;
    }

    pair<LL, LL> getValue() const {
        return make_pair(this->value, this->index);
    }

private:
    LL value;
    LL index;
    static const pair<LL,LL> unitValue;
};
const pair<LL,LL> Node::unitValue = make_pair(INF_INT_MAX, (LL)-1);

template <class T>
class SegmentTree {
public:
    SegmentTree(int size = 1) {
        init(size);
    }

    void init(int size) {
        vec.clear();
        k = 1;
        while(k < size) {
            k *= 2;
        }
        for(int i = 0; i < 2*k; i++) {
            vec.push_back(T::unit());
        }
    }

    void update(int i, T x) { //iをxに変更する
        i += k-1;
        vec[i] = x;
        while(i > 0) {
            i = (i-1)/2;
            vec[i] = vec[i*2+1] + vec[i*2+2];
        }
    }

    T find(int l, int r) {
        return _find(l, r, 0, 0, k);
    }

private:
    vector<T> vec;
    int k;

    T _find(int l, int r, int k, int x, int y) {
        if (r <= x || y <= l) { //重なってない場合
            return T::unit();
        } else if (l <= x && y <= r) { //完全にかぶってる場合
            return vec[k];
        } else { //中途半端にかぶってる場合
            int mid = (x+y)/2;
            T lNode = _find(l, r, 2*k+1, x, mid);
            T rNode = _find(l, r, 2*k+2, mid, y);
            return lNode + rNode;
        }
    }
};

using II = pair<int, int>;

const int MAX_N = 200005;
int N;
int P[MAX_N];
SegmentTree<Node> sg[2];

class PQNode {
public:
  PQNode(int l = 0, int r = 0, int value = -1) : l(l), r(r), value(value) {}
  int l, r, value;
  bool operator < (const PQNode& pqNode) const {
    return value < pqNode.value;
  } 
  bool operator > (const PQNode& pqNode) const {
    return value > pqNode.value;
  } 
};

signed main()
{
  cin >> N;
  
  sg[0].init(N); sg[1].init(N);
  
  REP(i,N) {
    cin >> P[i];
    Node n(make_pair(P[i], i));
    sg[i%2].update(i,n);
  }

  vector<int> ans;
  priority_queue<PQNode, vector<PQNode>, greater<PQNode>> pq;
  pq.push(PQNode(0, N, sg[0].find(0,N).getValue().first));

  while(pq.size()) {
    auto p = pq.top(); pq.pop();
    int l = p.l, r = p.r;
    if(r-l <= 0) {
      continue;
    }
    int i = sg[l%2].find(l,r).getValue().second;
    int j = sg[(i+1)%2].find(i+1,r).getValue().second;
    ans.push_back(P[i]);
    ans.push_back(P[j]);
    pq.push(PQNode(l,i,sg[l%2].find(l,i).getValue().first));
    pq.push(PQNode(i+1,j,sg[(i+1)%2].find(i+1,j).getValue().first));
    pq.push(PQNode(j+1,r,sg[(j+1)%2].find(j+1,r).getValue().first));
  }

  for(int i = 0; i < ans.size(); i++) {
    cout << ans[i];
    if(i < ans.size()-1) {
      cout << " ";
    }
  }
  cout << endl;

  return 0;
}

Measured memory_bytes: 31720