#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define all(c) (c).begin(),(c).end()
#define pb push_back
#define dbg(...) do{cerr<<__LINE__<<": ";dbgprint(#__VA_ARGS__, __VA_ARGS__);}while(0);

using namespace std;

namespace std{template<class S,class T>struct hash<pair<S,T>>{size_t operator()(const pair<S,T>&p)const{return ((size_t)1e9+7)*hash<S>()(p.first)+hash<T>()(p.second);}};template<class T>struct hash<vector<T>>{size_t operator()(const vector<T> &v)const{size_t h=0;for(auto i : v)h=h*((size_t)1e9+7)+hash<T>()(i)+1;return h;}};}
template<class T>ostream& operator<<(ostream &os, const vector<T> &v){os<<"[ ";rep(i,v.size())os<<v[i]<<(i==v.size()-1?" ]":", ");return os;}template<class T>ostream& operator<<(ostream &os,const set<T> &v){os<<"{ "; for(const auto &i:v)os<<i<<", ";return os<<"}";}
template<class T,class U>ostream& operator<<(ostream &os,const map<T,U> &v){os<<"{";for(const auto &i:v)os<<" "<<i.first<<": "<<i.second<<",";return os<<"}";}template<class T,class U>ostream& operator<<(ostream &os,const pair<T,U> &p){return os<<"("<<p.first<<", "<<p.second<<")";}
void dbgprint(const string &fmt){cerr<<endl;}template<class H,class... T>void dbgprint(const string &fmt,const H &h,const T&... r){cerr<<fmt.substr(0,fmt.find(","))<<"= "<<h<<" ";dbgprint(fmt.substr(fmt.find(",")+1),r...);}
typedef long long ll;typedef vector<int> vi;typedef pair<int,int> pi;const int inf = (int)1e9;const double INF = 1e12, EPS = 1e-9;

template<class T>struct SegTree{
	T *dat;
	int n;
	SegTree(int size = 1000000){
		for(n = 1; n < size; n *= 2);
		dat = new T[2 * n - 1];
		init();
	}
	~SegTree(){ delete [] dat; }
	
	void init(){
		rep(i, 2 * n - 1) dat[i] = pi(inf, -1);
	}
	void update(int k, T a){
		k += n - 1;
		dat[k] = a;
		
		while(k > 0){
			k = (k - 1) / 2;
			dat[k] = min(dat[k * 2 + 1], dat[k * 2 + 2]);
		}
	}
	T query(int a, int b, int k, int l, int r){
		if(r <= a || b <= l) return pi(inf, -1);
		if(a <= l && r <= b) return dat[k];
		
		T vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
		T vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
		
		return min(vl, vr);
	}
	T query(int a, int b){ return query(a, b, 0, 0, n); }
};

int main(){
	cin.tie(0); cin.sync_with_stdio(0);
	
	int n; cin >> n;
	SegTree<pi> even(n), odd(n);
	rep(i, n){
		int p; cin >> p;
		if(i % 2) odd.update(i, pi(p, i));
		else even.update(i, pi(p, i));
	}
	auto calc = [&](int l, int r){
		if(l % 2){
			pi x = odd.query(l, r);
			pi y = even.query(x.second, r);
			return pair<pi,pi>(x, y);
		}
		else{
			pi x = even.query(l, r);
			pi y = odd.query(x.second, r);
			return pair<pi,pi>(x, y);
		}
	};
	
	priority_queue<pair<int, pi>> q;
	q.emplace(-calc(0, n).first.first, pi(0, n));
	vi ans;
	while(!q.empty()){
		pi p = q.top().second; q.pop();
		int a = p.first, d = p.second;
		auto tmp = calc(a, d);
		ans.pb(tmp.first.first);
		ans.pb(tmp.second.first);
		
		int b = tmp.first.second, c = tmp.second.second;
		if(a < b) q.emplace(-calc(a, b).first.first, pi(a, b));
		if(b + 1 < c) q.emplace(-calc(b + 1, c).first.first, pi(b + 1, c));
		if(c + 1 < d) q.emplace(-calc(c + 1, d).first.first, pi(c + 1, d));
	}
	rep(i, n) cout << ans[i] << (i==n-1?"\n":" ");
	
	return 0;
}

Measured memory_bytes: 11176