#include <bits/stdc++.h>
using namespace std;
//#include<atcoder/all>
//using namespace atcoder;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
constexpr ll MAX = 2000000000000000000;
constexpr ld PI = 3.14159265358979;
constexpr ll MOD = 0;//2024948111;
ld dotorad(ld K){ return PI * K / 180.0; }
ld radtodo(ld K){ return K * 180.0 / PI; }
mt19937 mt;
void randinit(){ srand((unsigned)time(NULL));mt = mt19937(rand()); }
int main(){
    ll N;
    cin >> N;
    set<tuple<ll,ll>> st;
    vector<ll> A(N),doko(N + 1),ans;
    for(ll i = 0; i < N; i++){
        cin >> A[i];
        doko[A[i]] = i;
        st.insert({i,A[i]});
    }
    for(ll i = 1;i <= N;i++){
        auto p = st.lower_bound({doko[i],i});
        if(p == st.end()) continue;
        if(*p != make_tuple(doko[i],i)) continue;
        auto q = p;
        q++;
        if(q == st.end()) continue;
        ll x = i,y = get<1>(*q);
        st.erase(p);
        st.erase(q);
        ans.emplace_back(x);
        ans.emplace_back(y);
    }
    for(ll i = 0;i < (ll)ans.size();i++){
        cout << ans[i] << " \n"[i == (ll)ans.size() - 1];
    }
}