#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for(ll i = (a); i < (b); ++i)
#define FORR(i, a, b) for(ll i = (a); i > (b); --i)
#define REP(i, n) for(ll i = 0; i < (n); ++i)
#define REPR(i, n) for(ll i = n; i >= 0; i--)
#define FOREACH(x, a) for(auto &(x) : (a))
#define VECCIN(x)                                                              \
    for(auto &youso_ : (x)) cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) __builtin_clzll(x)
#define SZ(x) ((ll)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define PERM(c)                                                                \
    sort(All(c));                                                              \
    for(bool cp = true; cp; cp = next_permutation(All(c)))
#define MKORDER(n)                                                             \
    vector<ll> od(n);                                                          \
    iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
    T x;
    cin >> x;
    return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&... tail) {
    cin >> head;
    CIN(move(tail)...);
}
#define CCIN(...)                                                              \
    char __VA_ARGS__;                                                          \
    CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
    double __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
    ll __VA_ARGS__;                                                            \
    CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
    string __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
    {                                                                          \
        FOREACH(x, v) { cout << x << " "; }                                    \
        cout << "\n";                                                          \
    }
template <typename T = string> inline void eputs(T s) {
    cout << s << "\n";
    exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}

// generic lambdas
template <typename F>
#if defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
[[nodiscard]]
#elif defined(__GNUC__) &&                                                     \
    (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 4)
__attribute__((warn_unused_result))
#endif // defined(__has_cpp_attribute) && __has_cpp_attribute(nodiscard)
    static inline constexpr decltype(auto)
    fix(F &&f) noexcept {
    return [f = std::forward<F>(f)](auto &&... args) {
        return f(f, std::forward<decltype(args)>(args)...);
    };
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 1e18;
const double PI = atan(1.0) * 4.0;
const ll dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

//うし木 0-indexed
template <typename T, typename E> struct SegmentTree {
    typedef function<T(T, T)> F;
    typedef function<T(T, E)> G;
    int n;
    F f;
    G g;
    T e1;
    vector<T> dat;
    SegmentTree(){};
    SegmentTree(int n_, F f, G g, T e1, vector<T> v = vector<T>())
        : f(f), g(g), e1(e1) {
        init(n_);
        if(n_ == (int)v.size()) build(n_, v);
    }
    void init(int n_) {
        n = 1;
        while(n < n_) n *= 2;
        dat.clear();
        dat.resize(2 * n - 1, e1);
    }
    void build(int n_, vector<T> v) {
        for(int i = 0; i < n_; i++) dat[i + n - 1] = v[i];
        for(int i = n - 2; i >= 0; i--)
            dat[i] = f(dat[i * 2 + 1], dat[i * 2 + 2]);
    }
    void update(int k, E a) {
        k += n - 1;
        dat[k] = g(dat[k], a);
        while(k > 0) {
            k = (k - 1) / 2;
            dat[k] = f(dat[k * 2 + 1], dat[k * 2 + 2]);
        }
    }
    inline T query(int a, int b) {
        T vl = e1, vr = e1;
        for(int l = a + n, r = b + n; l < r; l >>= 1, r >>= 1) {
            if(l & 1) vl = f(vl, dat[(l++) - 1]);
            if(r & 1) vr = f(dat[(--r) - 1], vr);
        }
        return f(vl, vr);
    }
};

VL x(2);
VL pa;
VVL G;

signed main() {
    LCIN(N);
    VL p(N);
    G.resize(N + 1);
    pa.resize(N + 1);
    VECCIN(p);
    PL e1 = {LINF, LINF};
    auto f = [](PL a, PL b) { return min(a, b); };
    auto g = [](PL a, PL b) { return b; };
    using seg = SegmentTree<PL, PL>;
    vector<seg> segs(2, seg(N + 1, f, g, e1, VPL(N + 1, e1)));
    REP(i, N) { segs[i % 2].update(i, {p[i], i}); }
    auto dfs = fix([&](auto f, int l, int r, int idx) -> void {
        if(l + 1 >= r) {
            return;
        }
        PL p = segs[l % 2].query(l, r - 1);
        PL q = segs[(l % 2) ^ 1].query(p.se + 1, r);
        ll lr = p.se;
        ll rl = q.se;

        G[idx].emplace_back(p.fi);
        pa[p.fi] = q.fi;

        if(lr != l) f(f, l, lr, p.fi);
        if(lr + 1 != rl) f(f, lr + 1, rl, p.fi);
        if(rl + 1 != r) f(f, rl + 1, r, p.fi);
    });
    dfs(0, N, 0);
    VL ans;
    PQG<ll> pq;
    pq.push(G[0].front());
    while(pq.size()) {
        ll t = pq.top();
        pq.pop();

        ans.emplace_back(t);
        ans.emplace_back(pa[t]);

        FOREACH(to, G[t]) pq.push(to);
    }
    Printv(ans);
}


Measured memory_bytes: 88720