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

// template {{{
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define lb lower_bound
#define ub upper_bound
#define f first
#define s second

#define sz(x) int((x).size())
#define all(x) (x).begin(), (x).end()

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto& a : x)

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vd = vector<double>;
using vs = vector<string>;

template<typename T> void ckmin(T& a, const T& b) { a = min(a, b); }
template<typename T> void ckmax(T& a, const T& b) { a = max(a, b); }

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

namespace __input {
    template<class T1, class T2> void re(pair<T1,T2>& p);
    template<class T> void re(vector<T>& a);
    template<class T, size_t SZ> void re(array<T,SZ>& a);

    template<class T> void re(T& x) { cin >> x; }
    void re(double& x) { string t; re(t); x = stod(t); }
    template<class Arg, class... Args> void re(Arg& first, Args&... rest) {
        re(first); re(rest...);
    }

    template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
    template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
    template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}
using namespace __input;

namespace __output {
    template<class T1, class T2> void pr(const pair<T1,T2>& x);
    template<class T, size_t SZ> void pr(const array<T,SZ>& x);
    template<class T> void pr(const vector<T>& x);
    template<class T> void pr(const set<T>& x);
    template<class T1, class T2> void pr(const map<T1,T2>& x);

    template<class T> void pr(const T& x) { cout << x; }
    template<class Arg, class... Args> void pr(const Arg& first, const Args&... rest) {
        pr(first); pr(rest...);
    }

    template<class T1, class T2> void pr(const pair<T1,T2>& x) {
        pr("{",x.f,", ",x.s,"}");
    }
    template<class T> void prContain(const T& x) {
        pr("{");
        bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0;
        pr("}");
    }
    template<class T, size_t SZ> void pr(const array<T,SZ>& x) { prContain(x); }
    template<class T> void pr(const vector<T>& x) { prContain(x); }
    template<class T> void pr(const set<T>& x) { prContain(x); }
    template<class T1, class T2> void pr(const map<T1,T2>& x) { prContain(x); }

    void ps() { pr("\n"); }
    template<class Arg> void ps(const Arg& first) {
        pr(first); ps();
    }
    template<class Arg, class... Args> void ps(const Arg& first, const Args&... rest) {
        pr(first," "); ps(rest...);
    }
}
using namespace __output;

#define TRACE(x) x
#define __pn(x) pr(#x, " = ")
#define pd(...) __pn((__VA_ARGS__)), ps(__VA_ARGS__)

namespace __io {
    void setIn(string s) { freopen(s.c_str(),"r",stdin); }
    void setOut(string s) { freopen(s.c_str(),"w",stdout); }
    void setIO(string s = "") {
        ios_base::sync_with_stdio(0); cin.tie(0);
        if (sz(s)) { setIn(s+".in"), setOut(s+".out"); }
    }
}
using namespace __io;
// }}}

/*
 * Supports O(1) range queries on an immutable array of items.
 * Requires that type T's combine operator is associate, commutative,
 * and idempotent.
 */
template<typename T> struct sparse_table {
    int S, L;
    vector<T> table;
    T& entry(int l, int i) { return table[l * S + i]; }
    const T& entry(int l, int i) const { return table[l * S + i]; }

    sparse_table() {}
    sparse_table(const vector<T>& elts) : S(sz(elts)) {
        L = 32 - __builtin_clz(max(S - 1, 1));
        table.resize(L * S);
        copy(all(elts), table.begin());

        for (int l = 0; l + 1 < L; l++) {
            for (int i = 0; i < S; i++) {
                entry(l + 1, i) = entry(l, i);
                if (i + (1 << l) < S)
                    entry(l + 1, i) = entry(l + 1, i) + entry(l, i + (1 << l));
            }
        }
    }

    // Accumulates the elements at indices in [i, j) in O(1)
    T operator()(int i, int j) const {
        if (i >= j) return T{};
        int l = j - i - 1 ? 31 - __builtin_clz(j - i - 1) : 0;
        return entry(l, i) + entry(l, j - (1 << l));
    }
};
struct item {
    pair<int, int> me, mo;
    item(pair<int, int> _me, pair<int, int> _mo) : me(_me), mo(_mo) {}
    item(int i = INT_MAX, int v = INT_MAX) {
        mo =   i&1  ? mp(v , i) : mp(INT_MAX, INT_MAX);
        me = !(i&1) ? mp(v , i) : mp(INT_MAX, INT_MAX);
    }
    item operator+(const item& o) const {
        return item{ min(me, o.me), min(mo, o.mo) };
    }
};

int main() {
    setIO();

    int N; re(N);

    vector<item> p(N);
    F0R (i, N) {
        int v; re(v);
        p[i] = item(i, v);
    }
    sparse_table<item> st(p);

    struct segment {
        int i, j, v0, i0, v1, i1;
        bool operator<(const segment& o) const {
            return mp(v0, v1) > mp(o.v0, o.v1);
        }
    };
    auto calc = [&](int i, int j) {
        auto q0 = st(i, j); pair<int, int> v0 = i&1 ? q0.mo : q0.me;
        auto q1 = st(v0.s, j); pair<int, int> v1 = i&1 ? q1.me : q1.mo;
        return segment{ i, j, v0.f, v0.s, v1.f, v1.s };
    };

    priority_queue<segment> pq;
    pq.push(calc(0, N));

    vector<pair<int, int>> ans;
    while (!pq.empty()) {
        segment s = pq.top(); pq.pop();
        ans.eb(s.v0, s.v1);
        if (s.i0 != s.i) pq.push(calc(s.i, s.i0));
        if (s.i0 + 1 != s.i1) pq.push(calc(s.i0 + 1, s.i1));
        if (s.i1 + 1 != s.j) pq.push(calc(s.i1 + 1, s.j));
    }

    bool f = true;
    trav (v, ans) {
        if (!f) pr(" ");
        pr(v.f, " ", v.s);
        f = false;
    }
    ps();

    return 0;
}



Measured memory_bytes: 63668