#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (Y)-1;(X) >= (S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
#define out(args...){vector<string> a_r_g_s=s_p_l_i_t(#args, ','); e_r_r(a_r_g_s.begin(), args); }
vector<string> s_p_l_i_t(const string &s, char c){vector<string> v;int d=0,f=0;string t;for(char c:s){if(!d&&c==',')v.pb(t),t="";else t+=c;if(c=='\"'||c=='\'')f^=1;if(!f&&c=='(')++d;if(!f&&c==')')--d;}v.pb(t);return move(v);}
void e_r_r(vector<string>::iterator it) {}
template<typename T, typename... Args> void e_r_r(vector<string>::iterator it, T a, Args... args){ if(*it==" 1"||*it=="1") cerr<<endl; else cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << ", "; e_r_r(++it, args...);}
const ll MOD=1e9+7;

template<class T> class RMQ{
  vv<T> vals;
public:
  inline T get(int l,int r){//[l,r]
    if(l==r)return vals[0][l];
    const int d=31-__builtin_clz(l^r); //left-most distinct bit
    return min(vals[d][l],vals[d][r]);
  }
  RMQ(vector<T> &v,T e=-MOD){
    int n=v.size();
    int d=1,N=2;
    while(N<n) N*=2, ++d;
    vals.resize(d,vector<T>(N,e));
    rep(i,n) vals[0][i]=v[i];
    reps(i,1,d)rep(j,N){
      const int b=(j>>i|1)<<i;
      vals[i][j]=j>>i&1?get(b,j):get(j,b-1);
    }
  }
};

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
	int n;
	cin>>n;
	vector<int> a(n);
	rep(i,n) cin>>a[i];
	vector<pii> eve(n,pii(MOD,-1)),odd(n,pii(MOD,-1));
	rep(i,n) (i%2?odd:eve)[i]=pii(a[i],i);
	RMQ<pii> rmq0(eve,pii(MOD,-1));
	RMQ<pii> rmq1(odd,pii(MOD,-1));
	//out(eve,odd,1);
	typedef tuple<pii,pii,pii> TP;
	priority_queue<TP,vector<TP>, greater<TP>> que;
	auto fun=[&](int l,int r){
		pii p=(l%2?rmq1:rmq0).get(l,r-1);
		//out(l,r,p,1);
		pii q=(l%2?rmq0:rmq1).get(p.Y,r-1);
		return make_pair(p,q);
	};
	{
		pii a,b;
		tie(a,b)=fun(0,n);
		que.emplace(a,b,pii(0,n));
	}
	vector<int> re;
	while(que.size()){
		pii p,q,I; tie(p,q,I)=que.top(); que.pop();
		//out(p,q,I,1);
		re.pb(p.X); re.pb(q.X);
		int l=p.Y, r=q.Y;
		for(pii J:vector<pii>{{I.X, p.Y},{p.Y+1, q.Y},{q.Y+1, I.Y}}){
			if(J.Y-J.X<2) continue;
			pii a,b; tie(a,b)=fun(J.X, J.Y);
			que.emplace(a,b,J);
		}
	}
	for(int x:re) cout<<x<<" ";
  return 0;
}


Measured memory_bytes: 82556