// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;



#define for_(i,a,b) for(int i=(a);i<(b);++i)

#define for_rev(i,a,b) for(int i=(a);i>=(b);--i)

#define allof(a) (a).begin(),(a).end()

typedef long long lint;

typedef pair< int, int > pii;

template< typename T > using Vec = vector< T >;



class SegmentTree {

private:

	int size__;

	Vec< pii > data;

	

	inline int left_t(int k) { return (k << 1) + 1; }

	inline int right_t(int k) { return (k << 1) + 2; }

	inline int center(int l, int r) { return (l + r) >> 1; }

	

	pii calc(pii d1, pii d2) { return min(d1, d2); }

	

	pii query(int a, int b, int k, int l, int r) {

		if (r <= a || b <= l) return pii(1e9, 1e9);

		if (a <= l && r <= b) return data[k];

		return calc(query(a, b, left_t(k), l, center(l, r)),

					query(a, b, right_t(k), center(l, r), r));

	}

	

public:

	SegmentTree() {}

	

	SegmentTree(int n) {

		for (size__ = 1; size__ < n; size__ <<= 1);

		data.assign(2 * size__ - 1, pii(1e9, 1e9));

	}

	

	void update(int k, pii a) {

		k += size__ - 1;

		data[k] = a;

		

		while (k > 0) {

			k = (k - 1) >> 1;

			data[k] = calc(data[left_t(k)], data[right_t(k)]);

		}

	}

	

	pii query(int a, int b) { return query(a, b, 0, 0, size__); }

};



int N;

SegmentTree seg[2];



int m;

Vec< pii > piece;

Vec< int > nxt[200010];

map< pii, int > piece_to_id;



void divide(int l, int r, int par) {

	if (l >= r) return;

	

	pii a = seg[l % 2].query(l, r-1);

	pii b = seg[(l + 1) % 2].query(a.second+1, r);

	

	if (par != -1) nxt[par].push_back(m);

	piece.push_back(pii(a.first, b.first));

	piece_to_id[pii(a.first, b.first)] = m;

	int new_par = m;

	++m;

	

	if (l < a.second) divide(l, a.second, new_par);

	divide(a.second + 1, b.second, new_par);

	if (b.second + 1 < r) divide(b.second + 1, r, new_par);

}



void divideStack() {

	struct STK { int l, r, par; };

	

	stack< STK > stk;

	stk.push(STK{0, N, -1});

	

	while (!stk.empty()) {

		STK s = stk.top(); stk.pop();

		int l = s.l, r = s.r, par = s.par;

		if (l >= r) continue;

		

		pii a = seg[l % 2].query(l, r-1);

		pii b = seg[(l + 1) % 2].query(a.second+1, r);

		

		if (par != -1) nxt[par].push_back(m);

		piece.push_back(pii(a.first, b.first));

		piece_to_id[pii(a.first, b.first)] = m;

		

		if (l < a.second) stk.push(STK{l, a.second, m});

		stk.push(STK{a.second + 1, b.second, m});

		if (b.second + 1 < r) divide(b.second + 1, r, m);

		

		++m;

	}

}



int main() {

	cin >> N;

	

	for_(i,0,2) seg[i] = SegmentTree(N);

	

	for_(i,0,N) {

		int p; cin >> p;

		seg[i % 2].update(i, pii(p, i));

	}

	

	m = 0;

	divide(0, N, -1);

	//divideStack();

	

	Vec< int > ans;

	priority_queue< pii, Vec< pii >, greater< pii > > que;

	que.push(piece[0]);

	

	while (!que.empty()) {

		pii p = que.top(); que.pop();

		ans.push_back(p.first);

		ans.push_back(p.second);

		

		int id = piece_to_id[p];

		for (int i : nxt[id]) que.push(piece[i]);

	}

	

	for_(i,0,N) cout << ans[i] << (i < N - 1 ? " " : "\n");

}

// Faster C++ solution for the same problem (measured speedup: 1.831064371596048x):
#include <bits/stdc++.h>

using namespace std;



#define for_(i,a,b) for(int i=(a);i<(b);++i)

#define for_rev(i,a,b) for(int i=(a);i>=(b);--i)

#define allof(a) (a).begin(),(a).end()

typedef long long lint;

typedef pair< int, int > pii;

template< typename T > using Vec = vector< T >;



class SegmentTree {

private:

	int size__;

	Vec< pii > data;

	

	inline int left_t(int k) { return (k << 1) + 1; }

	inline int right_t(int k) { return (k << 1) + 2; }

	inline int center(int l, int r) { return (l + r) >> 1; }

	

	pii calc(pii d1, pii d2) { return min(d1, d2); }

	

	pii query(int a, int b, int k, int l, int r) {

		if (r <= a || b <= l) return pii(1e9, 1e9);

		if (a <= l && r <= b) return data[k];

		return calc(query(a, b, left_t(k), l, center(l, r)),

					query(a, b, right_t(k), center(l, r), r));

	}

	

public:

	SegmentTree() {}

	

	SegmentTree(int n) {

		for (size__ = 1; size__ < n; size__ <<= 1);

		data.assign(2 * size__ - 1, pii(1e9, 1e9));

	}

	

	void update(int k, pii a) {

		k += size__ - 1;

		data[k] = a;

		

		while (k > 0) {

			k = (k - 1) >> 1;

			data[k] = calc(data[left_t(k)], data[right_t(k)]);

		}

	}

	

	pii query(int a, int b) { return query(a, b, 0, 0, size__); }

};



int N;

SegmentTree seg[2];



Vec< pii > piece;

Vec< int > nxt[100010];

map< pii, int > piece_to_id;



void divide(int l, int r, int par) {

	if (l >= r) return;

	

	pii a = seg[l % 2].query(l, r-1);

	pii b = seg[(l + 1) % 2].query(a.second+1, r);

	

	if (par != -1) nxt[par].push_back(piece.size());

	piece_to_id[pii(a.first, b.first)] = piece.size();

	piece.push_back(pii(a.first, b.first));

	

	int cur = piece.size() - 1;

	if (l < a.second) divide(l, a.second, cur);

	divide(a.second + 1, b.second, cur);

	if (b.second + 1 < r) divide(b.second + 1, r, cur);

}



int main() {

	cin >> N;

	

	for_(i,0,2) seg[i] = SegmentTree(N);

	

	for_(i,0,N) {

		int p; cin >> p;

		seg[i % 2].update(i, pii(p, i));

	}

	

	divide(0, N, -1);

	

	Vec< int > ans;

	priority_queue< pii, Vec< pii >, greater< pii > > que;

	que.push(piece[0]);

	

	while (!que.empty()) {

		pii p = que.top(); que.pop();

		ans.push_back(p.first);

		ans.push_back(p.second);

		

		int id = piece_to_id[p];

		for (int i : nxt[id]) que.push(piece[i]);

	}

	

	for_(i,0,N) cout << ans[i] << (i < N - 1 ? " " : "\n");

}