#ifndef ONLINE_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <cassert>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
//using mint = modint1000000007;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repu(i, s, t) for (int i = (int)(s); i < (int)(t); i++)
#define repd(i, s, t) for (int i = (int)(s)-1; i >= (int)(t); i--)
#define all(v) v.begin(), v.end()
void _u() { cerr << endl; } template <class H, class... T> void _u(H&& h, T&&... t) { cerr << h << ", "; _u(move(t)...); }
#define U(...) { cerr << #__VA_ARGS__ << ": "; _u(__VA_ARGS__); }
template<typename T> bool chmax(T &a, const T b) { if(a >= b) return false; a = b; return true; }
template<typename T> bool chmin(T &a, const T b) { if(a <= b) return false; a = b; return true; }
template<typename T> istream& operator>>(istream &in, vector<T> &a) { for(T &x: a) in >> x; return in; }
template<typename T> ostream& operator<<(ostream &out, const vector<T> &a) { for(const T &x: a) out << x << ' '; return out; }
const int di[] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const int dj[] = {0, 1, 0, -1, -1, 1, 1, -1, 0};


int main() {
    int n;
    cin >> n;
    vector<int> p(n);
    cin >> p;
    rep(i, n) p[i]--;

    vector<int> go(n, -1), back(n, -1);
    vector<bool> exist(n, true);
    rep(i, n-1) go[p[i]] = p[i+1], back[p[i+1]] = p[i];
    auto erase = [&](int x) {
        if(back[x] >= 0) go[back[x]] = go[x];
        if(go[x] >= 0) back[go[x]] = back[x];
        exist[x] = false;
    };
    vector<int> q;
    rep(i, n) {
        if(!exist[i]) continue;
        if(go[i] == -1) continue;
        q.push_back(i);
        q.push_back(go[i]);
        erase(go[i]);
        erase(i);
    }
    rep(i, n) q[i]++;
    cout << q << endl;
    return 0;
}