#include <bits/stdc++.h>
#include <sys/time.h>
using namespace std;

#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define repi(i,a,b) for(long long i = (long long)(a); i < (long long)(b); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define mt make_tuple
#define mp make_pair
#define ZERO(a) memset(a,0,sizeof(a))
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
#define exists find_if
#define forall all_of

using ll = long long; using vll = vector<ll>; using vvll = vector<vll>; using P = pair<ll, ll>;
using ld = long double;  using vld = vector<ld>; 
using vi = vector<int>; using vvi = vector<vi>; vll conv(vi& v) { vll r(v.size()); rep(i, v.size()) r[i] = v[i]; return r; }
using Pos = complex<double>;

template <typename T, typename U> ostream &operator<<(ostream &o, const pair<T, U> &v) {  o << "(" << v.first << ", " << v.second << ")"; return o; }
template<size_t...> struct seq{}; template<size_t N, size_t... Is> struct gen_seq : gen_seq<N-1, N-1, Is...>{}; template<size_t... Is> struct gen_seq<0, Is...> : seq<Is...>{};
template<class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch,Tr>& os, Tuple const& t, seq<Is...>){ using s = int[]; (void)s{0, (void(os << (Is == 0? "" : ", ") << get<Is>(t)), 0)...}; }
template<class Ch, class Tr, class... Args> 
auto operator<<(basic_ostream<Ch, Tr>& os, tuple<Args...> const& t) -> basic_ostream<Ch, Tr>& { os << "("; print_tuple(os, t, gen_seq<sizeof...(Args)>()); return os << ")"; }
ostream &operator<<(ostream &o, const vvll &v) { rep(i, v.size()) { rep(j, v[i].size()) o << v[i][j] << " "; o << endl; } return o; }
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U, typename V>  ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it; o << "]";  return o; }
vector<int> range(const int x, const int y) { vector<int> v(y - x + 1); iota(v.begin(), v.end(), x); return v; }
template <typename T> istream& operator>>(istream& i, vector<T>& o) { rep(j, o.size()) i >> o[j]; return i;}
string bits_to_string(ll input, ll n=64) { string s; rep(i, n) s += '0' + !!(input & (1ll << i)); reverse(all(s)); return s; }

template <typename T> unordered_map<T, ll> counter(vector<T> vec){unordered_map<T, ll> ret; for (auto&& x : vec) ret[x]++; return ret;};
string substr(string s, P x) {return s.substr(x.fi, x.se - x.fi); }
struct ci : public iterator<forward_iterator_tag, ll> { ll n; ci(const ll n) : n(n) { } bool operator==(const ci& x) { return n == x.n; } bool operator!=(const ci& x) { return !(*this == x); } ci &operator++() { n++; return *this; } ll operator*() const { return n; } };

size_t random_seed; namespace std { using argument_type = P; template<> struct hash<argument_type> { size_t operator()(argument_type const& x) const { size_t seed = random_seed; seed ^= hash<ll>{}(x.fi); seed ^= (hash<ll>{}(x.se) << 1); return seed; } }; }; // hash for various class
namespace myhash{ const int Bsizes[]={3,9,13,17,21,25,29,33,37,41,45,49,53,57,61,65,69,73,77,81}; const int xor_nums[]={0x100007d1,0x5ff049c9,0x14560859,0x07087fef,0x3e277d49,0x4dba1f17,0x709c5988,0x05904258,0x1aa71872,0x238819b3,0x7b002bb7,0x1cf91302,0x0012290a,0x1083576b,0x76473e49,0x3d86295b,0x20536814,0x08634f4d,0x115405e8,0x0e6359f2}; const int hash_key=xor_nums[rand()%20]; const int mod_key=xor_nums[rand()%20]; template <typename T> struct myhash{ std::size_t operator()(const T& val) const { return (hash<T>{}(val)%mod_key)^hash_key; } }; };
template <typename T> class uset:public std::unordered_set<T,myhash::myhash<T>> { using SET=std::unordered_set<T,myhash::myhash<T>>; public: uset():SET(){SET::rehash(myhash::Bsizes[rand()%20]);} };
template <typename T,typename U> class umap:public std::unordered_map<T,U,myhash::myhash<T>> { public: using MAP=std::unordered_map<T,U,myhash::myhash<T>>; umap():MAP(){MAP::rehash(myhash::Bsizes[rand()%20]);} };    

struct timeval start; double sec() { struct timeval tv; gettimeofday(&tv, NULL); return (tv.tv_sec - start.tv_sec) + (tv.tv_usec - start.tv_usec) * 1e-6; }
struct init_{init_(){ gettimeofday(&start, NULL); ios::sync_with_stdio(false); cin.tie(0); srand((unsigned int)time(NULL)); random_seed = RAND_MAX / 2 + rand() / 2; }} init__;

static const double EPS = 1e-14;
static const long long INF = 1e18;
static const long long mo = 1e9+7;
#define ldout fixed << setprecision(40) 

// スパーステーブル
// 構築O(n log n)
// クエリO(log (log n))
//
// rmq(i, j)    [i, j)の最小値・最大値を求める
struct SparseTable {
    // 構築時データ
    vector<ll> val;
    
    // max_flag==trueならRange Maximum Query
    // デフォルトMinimum
    bool max_flag;

    // table[i][j]: [i, i+2^j)の最小値を取る添字
    vector<vector<ll>> table;

    inline ll MSB(ll x) { return x>0?31-__builtin_clz(x):-1; }
    SparseTable(void){}
    SparseTable(const vector<ll> a, bool max_flag_ = false) : val(a), max_flag(max_flag_) {
        ll n = a.size(), ln = MSB(n);
        table = vector<vector<ll>>(n, vector<ll>(ln + 1,0));
        rep(i,n)
            table[i][0] = i;

        ll k = 1;
        rep(j, ln) {
            rep(i, n){
                ll id1 = table[i][j], id2 = (i+k<n)?table[i+k][j]:id1;
                table[i][j+1] = (max_flag ? (val[id1]>=val[id2]) : (val[id1]<=val[id2]))?id1:id2;
            }
            k <<= 1;
        }
    }

    inline ll rmqi(ll l, ll r){
        if (l >= r) return INF;
        ll ln = MSB(r-l);
        ll id1 = table[l][ln], id2 = table[r-(1<<ln)][ln];
        return (max_flag ? (val[id1]>=val[id2]) : (val[id1]<=val[id2]))?id1:id2;
    }

    inline ll rmq(ll l, ll r){ 
        if (l >= r) return max_flag ? 0 : INF;
        return val[rmqi(l,r)]; 
    }
};


SparseTable st_o;
SparseTable st_e;
ll n;
vll a;
struct eo_ {
    ll ei = 0;
    ll e = 0;
    ll oi = 0;
    ll o = 0;
    ll l = 0;
    ll r = 0;
    eo_(ll x, ll y, ll z, ll w, ll l_, ll r_) {ei=x;e=y;oi=z;o=w;l=l_;r=r_;};
    bool operator<( const eo_& right ) const {
        return e > right.e;
    }
};
using eo = struct eo_;
void print(eo x) {
    cout << x.ei << " " << x.e << " " << x.oi << " " << x.o << endl;
}

#if 0
eo get(ll i, ll j) {
//    cout << i << " " << j << endl;
//    assert(abs(i - j) % 2 == 0);
    ll m = INF;
    ll mh = -1;
    for (ll h = i; h < j; h += 2) {
        if (m > a[h]) {
            m = a[h];
            mh = h;
        }
    }
    ll m2 = INF;
    ll mh2 = -1;
    for (ll h = mh+1; h < j; h += 2) {
        if (m2 > a[h]) {
            m2 = a[h];
            mh2 = h;
        }
    }
    return eo(mh,m,mh2,m2,i,j);
}

#else
eo get(ll i, ll j) {
//    cout << "GET" << endl;
//    cout << i << " " << j << endl;
//    assert(abs(i - j) % 2 == 0);
//    cout << st_o.val << endl;
//    cout << st_e.val << endl;
    ll m, mh, m2, mh2;
    if (i % 2 == 0) {
        m = st_e.rmq(i/2, (j+1)/2);
        mh = st_e.rmqi(i/2, (j+1)/2) * 2;
    } else {
        m = st_o.rmq(i/2, j/2);
        mh = st_o.rmqi(i/2, j/2) * 2 + 1;
    }

    ll tmp = mh+1;
    if (tmp % 2 == 0) {
        m2 = st_e.rmq(tmp/2, (j+1)/2);
        mh2 = st_e.rmqi(tmp/2, (j+1)/2) * 2;
    } else {
        m2 = st_o.rmq(tmp/2, j/2);
        mh2 = st_o.rmqi(tmp/2, j/2) * 2 + 1;
    }

//    cout << mh << " " << m << " " << mh2 << " " << m2 << endl;
//    cout << "END GET" << endl;
    return eo(mh,m,mh2,m2,i,j);
}
#endif


vll ret;

int main(void) {
    cin >> n;
    a.resize(n);
    cin >> a;

    vll ao, ae;
    rep(i, n) {
        (i % 2 == 0 ? ae : ao).pb(a[i]); 
    }
    st_o = SparseTable(ao);
    st_e = SparseTable(ae);

//    dfs(0, n);
//    priority_queue<eo, vector<eo>, greater<eo>> q;
    priority_queue<eo> q;
    q.push(get(0, n));
    while (q.size()) {
        auto tmp = q.top(); q.pop();
        ll i = tmp.l, j = tmp.r;
        ll ei = tmp.ei;
        ll e = tmp.e;
        ll oi = tmp.oi;
        ll o = tmp.o;

//        cout << i << " " << j << "#ij" << endl;
//        cout << ei << " " << oi << "#eioi" << endl;
        ret.pb(e);
        ret.pb(o);

        vector<eo> cands;
        if (ei != i) q.push(get(i, ei));
        if (ei + 1 != oi) q.push(get(ei+1, oi));
        if (oi + 1 != j) q.push(get(oi+1, j));
//        cout << cands << endl;
    }

    rep(i, n) {
        cout << ret[i] << " ";
    }
    cout << endl;
    return 0;
}


Measured memory_bytes: 45272