#include<bits/stdc++.h>
#define ll int
#define pll pair<ll, ll>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ld long double
#define sz(a) ((ll)(a).size())
using namespace std;

const ll inf=1e9;
vector<pair<int, int>> min_shooting_buildings(vector<int> a)
{
    ll n=sz(a);
    vector <pll> p;
    vector <ll> ok, pos(n+1, 0);
    for (ll i=0; i<n; i++) pos[a[i]]=i;
    for (ll i=0; i<n; i++)
    {
        ll Max=0;
        for (ll j:ok)
            if (j<=a[i])
                Max=max(Max, j);
        if (Max)
        {
            p.pb({Max, a[i]});
            for (ll& j:ok)
                if (j==Max)
                {
                    swap(j, ok.back()), ok.pop_back();
                    break;
                }
            continue;
        }
        pair<int, int> Min={inf, inf};
        for (pll j:p)
        {
            if (j.se<=a[i])
                Min=min(Min, j);
            if (j.fi<=a[i])
                Min=min(Min, {j.se, j.fi});
        }
        if (Min.fi!=inf)
        {
            p.pb({Min.se, a[i]}), ok.pb(Min.fi);
            if (Min.fi>Min.se) swap(Min.fi, Min.se);
            for (pll& j:p)
                if (j==Min)
                {
                    swap(j, p.back()), p.pop_back();
                    break;
                }
        }
        else ok.pb(a[i]);
    }
    vector <pll> ans;
    for (pll& i:p) i={pos[i.fi], pos[i.se]}; 
    for (ll i:ok) p.pb({pos[i], pos[i]});
    sort(p.begin(), p.end());
    for (ll i=0; i<sz(p); i++)
        for (ll j=0; j<i; j++)
        {
            if (p[j].fi<p[i].fi && p[i].se<p[j].se)
            {
                if (a[p[i].se]>a[p[j].fi] && a[p[j].se]>a[p[i].fi])
                    swap(p[i].se, p[j].se);
            }
            else if (p[i].fi<p[j].fi && p[j].se<p[i].se)
            {
                if (a[p[j].se]>a[p[i].fi] && a[p[i].se]>a[p[j].fi])
                    swap(p[i].se, p[j].se);
            }
        }
    vector <bool> check(sz(p), 0);
    for (ll i=0; i<sz(p); i++)
    {
        for (ll j=0; j<sz(p); j++)
        {
            if (check[j]) continue;
            auto [p1, p2]=p[j];
            bool ok=1;
            for (ll k=0; k<p1; k++)
                if (a[k]>a[p1]) ok=0;
            for (ll k=0; k<p2; k++)
                if (a[k]>a[p2]) ok=0;
            if (ok)
            {
                ans.pb({a[p[j].fi], a[p[j].se]}), check[j]=1, a[p1]=a[p2]=0;
                break;
            }
        }
    }
    return ans;
}