#define STOPIT
#include <bits/stdc++.h>
#define loop(n) for (lint ngtkana_is_a_genius = 0; ngtkana_is_a_genius < lint(n); ngtkana_is_a_genius++)
#define rep(i, begin, end) for (lint i = lint(begin); (i) < lint(end); i++)
#define all(v) v.begin(), v.end()
#define rand(l, r) std::uniform_int_distribution<>(l, r)(mt)
using lint = long long;
auto mt = std::mt19937_64(std::random_device{}());
auto cmn = [](auto& a, auto b){ if (a > b) {a = b; return true;} return false; };
auto cmx = [](auto& a, auto b){ if (a < b) {a = b; return true;} return false; };
void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#ifndef STOPIT
#define debug(...)\
	do {\
		std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
		debug_impl(__VA_ARGS__);\
		std::cerr << std::noboolalpha;\
	} while (false)
#else
#define debug(...) {}
#endif

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr>
std::istream& operator>> (std::istream& is, Container& v)
	{ for (auto & x : v) { is >> x; } return is; }

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr >
std::ostream& operator<< (std::ostream& os, Container const& v) {
 os << "{";
	for (auto it = v.begin(); it != v.end(); it++)
		{os << (it != v.begin() ? "," : "") << *it;}
	return os << "}";
}

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& tuple_input_impl(std::istream& os, Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
	{ (void)std::initializer_list<int>{((void)(os >> std::get< Inds >(tuple)), 0)...}; return os; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& operator>> (std::istream& os, Tuple<Args...>& tuple)
	{ return tuple_input_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& tuple_output_impl(std::ostream& os, const Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
	{ os << "("; (void)std::initializer_list<int>{((void)(os << (Inds > 0 ? "," : "") << std::get< Inds >(tuple)), 0)...}; return os << ")"; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& operator<< (std::ostream& os, const Tuple<Args...>& tuple)
 { return tuple_output_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < typename Value, typename BinaryOp >
class segment_tree {
		int                  sz, n, N;
		BinaryOp             op;
		Value                id;
		std::vector< Value > table;

		auto& op_eq(Value& x, Value y) const
			{ return x = op(x, y); }
		void merge(int u)
			{ table.at(u) = op(table.at(2 * u), table.at(2 * u + 1)); }

	public:
		segment_tree(int sz, BinaryOp op, Value id):
			sz    (sz),
			n     (std::pow(2, int(std::log2(2 * sz - 1)))),
			N     (n * 2),
			op    (op),
			id    (id),
			table (N, id)
			{}

		auto& at(int i)       { return table.at(n + i); }
		auto& at(int i) const { return table.at(n + i); }
		auto collect() const {
			auto ret = std::vector<Value>(sz);
			for (auto i = 0; i < sz; i++)
				{ ret.at(i) = at(i); }
			return ret;
		}
		auto query(int l, int r) const {
			auto const dfs = [&](auto&& f, int l, int r, int k, int L, int R) -> Value {
				return l <= L && R <= r
					? table.at(k)
					: R <= l || r <= L
					? id
					: op(
						f(f, l, r, 2 * k, L, (L + R) / 2),
						f(f, l, r, 2 * k + 1, (L + R) / 2, R)
					);
			};
			return dfs(dfs, l, r, 1, 0, n);
		}
		void build_oneline(int i)
			{ for (i += n, i /= 2; i > 0; i /= 2) merge(i); }
		void build()
			{ for (auto i = n - 1; i > 0; i--) merge(i); }
};

template<typename Value, typename BinaryOp>
auto make_segment_tree(int sz, BinaryOp op, Value id)
	{ return segment_tree<Value, BinaryOp>(sz, std::move(op), id); }

// require gcc >= 7.1.0
template < class ... Keys >
class fmt_t {
		using storage_t = std::tuple< Keys ... >;
		storage_t storage;
		static constexpr std::size_t N = sizeof ... (Keys);

		// is_exact_match_impl
		template < std::size_t I, class Value >
			auto is_exact_match_impl(long, Value) const
				{ return false; }

		template < std::size_t I, class Value,
			std::enable_if_t<
				std::is_same< std::decay_t< Value > , char >::value
				== std::is_same< std::tuple_element_t< I, storage_t >, char >::value,
			std::nullptr_t > = nullptr,
			class = decltype(std::declval< Value >() == std::get< I >(std::declval< storage_t >())) >
			auto is_exact_match_impl(int, Value x) const
				{ return x == std::get< I >(storage); }

		template < class Value, std::size_t ... Is >
			auto find_exact_match_impl(Value x, std::integer_sequence< std::size_t, Is ... >) const {
				auto ret = false;
				(void)std::initializer_list< std::nullptr_t >
					{ (ret |= is_exact_match_impl< Is >(int{}, x), nullptr) ...  };
				return ret;
			}

		template < class Value >
			auto exists_exact_match(Value x) const
			{  return find_exact_match_impl(x, std::make_index_sequence< N >()); }

		// tuple_format_impl
		template < class Tuple,  std::size_t ... Is >
		std::string tuple_format_impl(const Tuple& tuple, std::integer_sequence< std::size_t, Is ... >) const {
			std::string ret = "(";
			(void)std::initializer_list< std::nullptr_t >
				{ (ret = ret + (Is == 0 ? "" : ",") + format(std::get< Is >(tuple)), nullptr) ... };
			return ret + ")";
		}

		// usual_format
		template < class Value >
		std::string usual_format(long, Value x) const
			{ return std::to_string(x); }

		template < class Value, std::enable_if_t< std::is_same< std::decay_t< Value >, char >::value, std::nullptr_t > = nullptr >
		std::string usual_format(int, Value c) const
			{ return std::string{'\''} + std::string{c} + std::string{'\''}; }

		std::string usual_format(int, char const* s) const
			{ return "\"" + std::string(s) + "\""; }

		std::string usual_format(int, std::string const s) const
			{ return "\"" + s + "\""; }

		template < class Container, class = typename Container::value_type >
		std::string usual_format(int, Container const & v) const {
			return "{" + std::accumulate(v.begin(), v .end(), std::string{},
				[this](auto const& s, auto const x) { return s + (s.empty() ? "" : ",") + this->format(x); })
				+ "}";
		}

		template < class Tuple, std::size_t N = std::tuple_size< Tuple >::value >
		std::string usual_format(int, Tuple const& tuple) const
			{ return tuple_format_impl(tuple, std::make_index_sequence< N >()); }

		// format
		template < class Value > std::string format(Value&& x) const
			{ return exists_exact_match(x) ? std::string{'_'} : usual_format(int{}, x); }

	public:
		fmt_t()=default;
		template < Keys ... > fmt_t(Keys&& ... keys ) : storage(keys ... ){}

		template < class Value > std::string operator()(Value&& x) const
			{ return format(x); }
};
template < class ... Keys > auto fmt(Keys&& ... keys)
	{ return fmt_t< Keys ... >(std::forward< Keys >(keys) ... ); }

int main() {
	std::cin.tie(0); std::cin.sync_with_stdio(false);
	int n; std::cin >> n;
	std::vector<int> a(n); std::cin>> a;
	for (int& x : a) x--;
	std::vector<int> ainv(n);
	rep(i,0,n) ainv.at(a.at(i)) = i;
	debug(a,ainv);

	int inf = std::numeric_limits<int>::max();
	auto op = [](int x, int y){ return std::min(x,y); };
	auto seg = std::vector<segment_tree<int,decltype(op)>>(2, make_segment_tree(n, op, inf));
	rep(i,0,n) {
		seg.at(i%2).at(i) = a.at(i);
	}
	for (auto& s : seg) s.build();
	debug(fmt(inf)(seg.at(0).collect()));
	debug(fmt(inf)(seg.at(1).collect()));

	using tup = std::tuple<int,int,int,int>;
	std::priority_queue<tup, std::vector<tup>, std::greater<>> que;
	auto erase = [&] (int x) {
		debug("erase",x);
		seg.at(x%2).at(x) = inf;
		seg.at(x%2).build_oneline(x);
	};
	auto push = [&] (int l, int r) {
		debug("push lr",l,r);
		assert(l <= r && (r - l) % 2 == 0);
		if (l==r) return;
	  bool b = l % 2;
		int x = seg.at( b).query(l,r);
		int x_ = ainv.at(x);
		int y = seg.at(!b).query(x_+1,r);
		debug("push xy",x,y);
		que.emplace(x,y,l,r);
	};

	std::vector<int> ans;
	push(0,n);
	while (!que.empty()) {
		int x,y,l,r; std::tie(x,y,l,r) = que.top(); que.pop();
		ans.emplace_back(x);
		ans.emplace_back(y);
		debug(x,y,l,r);
		int x_ = ainv.at(x);
		int y_ = ainv.at(y);
		debug(x_,y_,l,r);
		erase(x_);
		erase(y_);
		push(l,x_);
		push(x_+1,y_);
		push(y_+1,r);
	}

	for (int & x : ans) x++;
	rep(i,0,n) {
		std::cout << (0 < i ? " " : "") << ans.at(i);
	}
	std::cout << std::endl;
	return 0;
}

Measured memory_bytes: 9596