#define _USE_MATH_DEFINES
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include<bits/stdc++.h>
#include<unordered_set>
#include<random>
#include <array>
#include <complex>
#include<chrono>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
#define LP(I,S,G) for (long long int I = (S); I < (G); ++I)
#define IN(X) 	for (int in = 0; in < X.size(); in++)cin >> X[in]
#define OUT(X) 	for (int in = 0; in < X.size(); in++)cout << X[in]<<" "
#define SORT(X) sort((X).begin(), (X).end())
#define CSORT(X,Y) sort(X.begin(), X.end(),Y)
#define COPY(X,Y) copy(X.begin(), X.end(), Y.begin())
#define ALL(X,Y) for (auto &(X) :(Y))
#define FULL(a)  (a).begin(),(a).end()
#define BFS(Q,S) for(Q.push(S);Q.size()!=0;Q.pop())
typedef long long int ll;
typedef unsigned long long int ull;
long long int M = 998244353;

chrono::system_clock::time_point starttime;
using namespace std::chrono;

inline float getTime() {
	return duration_cast<milliseconds>(system_clock::now() - starttime).count();
}


int dx[] = { -1,0,1,0 }, dy[] = { 0,1,0,-1 };

ll MAX(ll A, ll B) { return ((A) > (B) ? (A) : (B)); }
ll MIN(ll A, ll B) { return ((A) < (B) ? (A) : (B)); }
inline long long int xor128() {
	static long long int x = 123456789, y = 362436069, z = 521288629, w = 88675123;
	long long int t = (x ^ (x << 11));
	x = y; y = z; z = w;
	return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}

int main() {
	ll n;
	cin >> n;
	vector<ll> p(n), t(n + 1, 1), rev(n + 1, 0), ans;
	IN(p);
	set<ll> idx;
	LP(i, 0, n) {
		idx.insert(i);
		rev[p[i]] = i;
	}
	LP(i, 1, n+1) {
		if (t[i] == 0)continue;
		auto itr = idx.find(rev[i]);
		++itr;
		if (itr == idx.end())continue;
		ans.push_back(i);
		ans.push_back(p[*itr]);
		t[i] = 0;
		t[p[*itr]] = 0;
		idx.erase(itr);
		idx.erase(idx.find(rev[i]));
	}
	OUT(ans);
	return 0;
}