#include <algorithm>
#include <iostream>
#include <vector>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <set>

using namespace std;

namespace fastinput {
	/** Interface */

	template <class T = int> inline T readInt();
	inline double readDouble();
	inline int readUInt();
	inline int readChar();
	inline void readWord(char *s);
	inline bool readLine(char *s); // do not save '\n'
	inline bool isEof();
	inline int peekChar();
	inline bool seekEof();

	template <class T> inline void writeInt(T x, int len = -1);
	template <class T> inline void writeUInt(T x, int len = -1);
	inline void writeChar(int x);
	inline void writeWord(const char *s);
	inline void writeDouble(double x, int len = 0);
	inline void flush();

	/** Read */

	static const int buf_size = 4096;

	static char buf[buf_size];
	static int buf_len = 0, buf_pos = 0;

	inline bool isEof() {
		if (buf_pos == buf_len) {
			buf_pos = 0, buf_len = fread(buf, 1, buf_size, stdin);
			if (buf_pos == buf_len)
				return 1;
		}
		return 0;
	}

	inline int getChar() {
		return isEof() ? -1 : buf[buf_pos++];
	}

	inline int peekChar() {
		return isEof() ? -1 : buf[buf_pos];
	}

	inline bool seekEof() {
		int c;
		while ((c = peekChar()) != -1 && c <= 32)
			buf_pos++;
		return c == -1;
	}

	inline int readChar() {
		int c = getChar();
		while (c != -1 && c <= 32)
			c = getChar();
		return c;
	}

	inline int readUInt() {
		int c = readChar(), x = 0;
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return x;
	}

	template <class T>
	inline T readInt() {
		int s = 1, c = readChar();
		T x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return s == 1 ? x : -x;
	}

	inline double readDouble() {
		int s = 1, c = readChar();
		double x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		if (c == '.') {
			c = getChar();
			double coef = 1;
			while ('0' <= c && c <= '9')
				x += (c - '0') * (coef *= 1e-1), c = getChar();
		}
		return s == 1 ? x : -x;
	}

	inline void readWord(char *s) {
		int c = readChar();
		while (c > 32)
			*s++ = c, c = getChar();
		*s = 0;
	}

	inline bool readLine(char *s) {
		int c = getChar();
		while (c != '\n' && c != -1)
			*s++ = c, c = getChar();
		*s = 0;
		return c != -1;
	}

	/** Write */

	static int write_buf_pos = 0;
	static char write_buf[buf_size];

	inline void writeChar(int x) {
		if (write_buf_pos == buf_size)
			fwrite(write_buf, 1, buf_size, stdout), write_buf_pos = 0;
		write_buf[write_buf_pos++] = x;
	}

	inline void flush() {
		if (write_buf_pos)
			fwrite(write_buf, 1, write_buf_pos, stdout), write_buf_pos = 0;
	}

	template <class T>
	inline void writeInt(T x, int output_len) {
		if (x < 0)
			writeChar('-'), x = -x;

		char s[24];
		int n = 0;
		while (x || !n)
			s[n++] = '0' + x % 10, x /= 10;
		while (n < output_len)
			s[n++] = '0';
		while (n--)
			writeChar(s[n]);
	}

	template <class T>
	inline void writeUInt(T x, int output_len) {
		char s[24];
		int n = 0;
		while (x || !n)
			s[n++] = '0' + x % 10, x /= 10;
		while (n < output_len)
			s[n++] = '0';
		while (n--)
			writeChar(s[n]);
	}

	inline void writeWord(const char *s) {
		while (*s)
			writeChar(*s++);
	}

	inline void writeDouble(double x, int output_len) {
		if (x < 0)
			writeChar('-'), x = -x;
		int t = (int)x;
		writeUInt(t), x -= t;
		writeChar('.');
		for (int i = output_len - 1; i > 0; i--) {
			x *= 10;
			t = std::min(9, (int)x);
			writeChar('0' + t), x -= t;
		}
		x *= 10;
		t = std::min(9, (int)(x + 0.5));
		writeChar('0' + t);
	}
}

using namespace fastinput;

const int N = 2e5;

int a[N + 1];

//o o o o o o
//x x ^ x x ^ 

// algo (l..r)
// choose_best_pair(l..r)
// the array is split into pieces.
// order of their traversal depends on their best pair.

int evenMin[4 * N];
int oddMin[4 * N];
const int INF = 1e9;
int n;

void build(int i, int l, int r) {
	if (l == r) {
		if (l & 1) {
			oddMin[i] = n;
			evenMin[i] = l;
		} else {
			oddMin[i] = l;
			evenMin[i] = n;
		}
	} else {
		build(2 * i, l, (l + r) / 2);
		build(2 * i + 1, (l + r) / 2 + 1, r);
		int lef = oddMin[2 * i];
		int rig = oddMin[2 * i + 1];
		oddMin[i] = a[lef] < a[rig] ? lef : rig;
		lef = evenMin[2 * i];
		rig = evenMin[2 * i + 1];
		evenMin[i] = a[lef] < a[rig] ? lef : rig;
	}
}

int A, B;

int queryEven(int i, int l, int r) {
	if (l > B || r < A)
		return n;
	if (l >= A && r <= B)
		return evenMin[i];
	int lef = queryEven(2 * i, l, (l + r) / 2);
	int rig = queryEven(2 * i + 1, (l + r) / 2 + 1, r);
	return a[lef] < a[rig] ? lef : rig;
}

int queryOdd(int i, int l, int r) {
	if (l > B || r < A)
		return n;
	if (l >= A && r <= B)
		return oddMin[i];
	int lef = queryOdd(2 * i, l, (l + r) / 2);
	int rig = queryOdd(2 * i + 1, (l + r) / 2 + 1, r);
	return a[lef] < a[rig] ? lef : rig;
}

int Odd(int l, int r) {
	A = l, B = r;
	return queryOdd(1, 0, n - 1);
}

int Even(int l, int r) {
	A = l, B = r;
	return queryEven(1, 0, n - 1);
}

pair <int, int> choose_best_pair(int l, int r) {
	if (l > r) {
		return { n, n };
	}
	if ((l & 1) == 0) {
		//odd start
		int idl = Odd(l, r);
		int idr = Even(idl + 1, r);
		return { idl, idr };
	} else {
		//even start
		int idl = Even(l, r);
		int idr = Odd(idl + 1, r);
		return { idl, idr };
	}
}

struct tmp {
	pair <int, int> ans;
	pair <int, int> keep;
};

bool operator <(const tmp& l, const tmp& r) {
	return a[l.ans.first] < a[r.ans.first];
}

set <tmp> have;

tmp gather(int l, int r) {
	return { choose_best_pair(l, r),{ l, r } };
}

tmp arr[3];

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	n = readInt();
	for (int i = 0; i < n; ++i)
		a[i] = readInt();
	a[n] = INF;
	build(1, 0, n - 1);
	have.insert(gather(0, n - 1));
	while (!have.empty()) {
		tmp now = *have.begin();
		have.erase(have.begin());
		int l = now.keep.first;
		int r = now.keep.second;
		int idl = now.ans.first;
		int idr = now.ans.second;
		printf("%d %d ", a[idl], a[idr]);
		arr[0] = gather(l, idl - 1);
		arr[1] = gather(idl + 1, idr - 1);
		arr[2] = gather(idr + 1, r);
		sort(arr, arr + 3);
		for (int i = 0; i < 3; ++i) {
			if (arr[i].ans.first != n)
				have.emplace(std::move(arr[i]));
		}
	}
	return 0;
}

Measured memory_bytes: 11008