#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (((bit >> i) & 1) > 0)

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

// 2のべき乗数かどうか
bool is_power_of_two(long long x) {
    return !(x & (x - 1));
}

// aとbの最大公約数 O(log min(a, b))
long long gcd(long long a, long long b) {
    if (b == 0) { return a; }
    return gcd(b, a % b);
}

// 数列vの最大公約数 O(N log d)
long long gcd(std::vector<long long> &v) {
    long long ans = v[0];
    for (int i = 1; i < v.size(); ++i) {
        ans = gcd(ans, v[i]);
    }
    return ans;
}

// aとbの最小公倍数 O(log min(a, b))
long long lcm(long long a, long long b) {
    long long g = gcd(a, b);
    return a / g * b;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};  // 右，下
const std::vector<int> dy4 = {0, -1, 0, 1}, dx4 = {1, 0, -1, 0};    // 右，上，左，下
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };


using namespace std;

template <typename T> class SegmentTree {
    int array_size;        // もとの配列のサイズ
    int n;
    std::vector<T> data;
    std::function<T (T,T)> op;
    T unit;

public:
    enum Mode {
        RangeMinimumQuery,
        RangeMaximumQuery,
        RangeSummationQuery,
    };

    SegmentTree() {

    }

    void init(int array_size, Mode mode) {
        this->array_size = array_size;
        if (mode == RangeMinimumQuery) {
            unit = INT_MAX;
            op = [](T a, T b) { return std::min(a, b); };
        }
        else if (mode == RangeMaximumQuery) {
            unit = 0;
            op = [](T a, T b) { return std::max(a, b); };
        }
        else if (mode == RangeSummationQuery) {
            unit = 0;
            op = [](T a, T b) { return a + b; };
        }
        else {
            assert(false);
        }

        n = 1;
        while (n < array_size) { n *= 2; }   // _n以上の最小の2冪
        data.resize(2 * n - 1, unit);
    }

    template <typename F> SegmentTree(int array_size, T unit, F op) : array_size(array_size), unit(unit), op(op) {
        while (n < array_size) { n *= 2; }   // _n以上の最小の2冪
        data.resize(2 * n - 1, unit);
    }

    T access(int idx) {
        return data[idx + n - 1];
    }

    // array[idx] = x
    // O(log N)
    void update(int idx, T x) {
        assert(0 <= idx and idx < array_size);
        idx += n - 1;   // 木での対象のインデックス
        data[idx] = x;
        while (idx > 0) {
            idx = (idx - 1) / 2;                                    // 親のインデックス
            data[idx] = op(data[idx * 2 + 1], data[idx * 2 + 2]);   // 左の子と右の子
        }
    }

    // op(array[left, right))
    // O(log N)
    T query(int left, int right) {
        assert(0 <= left and left < right and right <= array_size);
        return query(left, right, 0, 0, n);
    }

private:
    // [a, b)の目的値をノードk（区間[l, r]）から検索
    T query(int a, int b, int k, int l, int r) {
        assert(a < b && l < r);
        // 範囲外
        if (r <= a || b <= l) {
            return unit;
        }
        // 完全に含む
        if (a <= l && r <= b) {
            return this->data.at(k);
        }
            // 一部含む
        else {
            T vl = query(a, b, k * 2 + 1, l, (l + r) / 2);    // 左の子
            T vr = query(a, b, k * 2 + 2, (l + r) / 2, r);    // 右の子
            return op(vl, vr);
        }
    }
};


void solve(int N, vector<int> &P) {

    unordered_map<int, int> value_idx;
    SegmentTree<int> odd, even;
    odd.init(N + 100, SegmentTree<int>::RangeMinimumQuery);
    even.init(N + 100, SegmentTree<int>::RangeMinimumQuery);
    FOR(i, 0, N) {
        value_idx[P[i]] = i;
        if (i % 2 == 0) {
            even.update(i, P[i]);
        }
        else {
            odd.update(i, P[i]);
        }
    }

    vector<int> ans;

    priority_queue<tuple<int, int, int>> pq;
    pq.push(make_tuple(INF, 0, N));

    while (not pq.empty()) {
        int k, l, r;
        tie(k, l, r) = pq.top(); pq.pop();

        if (l + 1 == r) {
            ans.emplace_back(P[l]);
            ans.emplace_back(P[r]);
            continue;
        }

        int mini = INF, mini_idx = -1;
        int mini2 = INF, mini_idx2 = -1;
        if (l % 2 == 0) {
            mini = even.query(l, r);
            mini_idx = value_idx[mini];
            even.update(mini_idx, INF);

            mini2 = odd.query(mini_idx + 1, r);
            mini_idx2 = value_idx[mini2];
            odd.update(mini_idx2, INF);
        }
        else {
            mini = odd.query(l, r);
            mini_idx = value_idx[mini];
            odd.update(mini_idx, INF);

            mini2 = even.query(mini_idx + 1, r);
            mini_idx2 = value_idx[mini2];
            even.update(mini_idx2, INF);
        }

        ans.emplace_back(mini);
        ans.emplace_back(mini2);

        int key = 0;
        if (mini_idx > l) {
            if (l % 2 == 0) {
                key = even.query(l, mini_idx);
            } else {
                key = odd.query(l, mini_idx);
            }
            pq.push(make_tuple(-key, l, mini_idx));
        }

        if (mini_idx2 > mini_idx + 1) {
            if ((mini_idx + 1) % 2 == 0) {
                key = even.query(mini_idx + 1, mini_idx2);
            } else {
                key = odd.query(mini_idx + 1, mini_idx2);
            }
            pq.push(make_tuple(-key, mini_idx + 1, mini_idx2));
        }

        if (r > mini_idx2 + 1) {
            if ((mini_idx2 + 1) % 2 == 0) {
                key = even.query(mini_idx2 + 1, r);
            } else {
                key = odd.query(mini_idx2 + 1, r);
            }
            pq.push(make_tuple(-key, mini_idx2 + 1, r));
        }
    }

    print_vec(ans);
}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    LL N;
    cin >> N;
    auto P = make_v<int>(N);
    FOR(i, 0, N) {
        cin >> P[i];
    }

    solve(N, P);


    return 0;
}


Measured memory_bytes: 16968