#include <bits/stdc++.h>
#define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

constexpr lint mod = 1000000007;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

#ifndef ATCODER_INTERNAL_BITOP_HPP
#define ATCODER_INTERNAL_BITOP_HPP 1

#ifdef _MSC_VER
#include <intrin.h>
#endif

namespace atcoder {

namespace internal {

// @param n `0 <= n`
// @return minimum non-negative `x` s.t. `n <= 2**x`
int ceil_pow2(int n) {
    int x = 0;
    while ((1U << x) < (unsigned int)(n)) x++;
    return x;
}

// @param n `1 <= n`
// @return minimum non-negative `x` s.t. `(n & (1 << x)) != 0`
int bsf(unsigned int n) {
#ifdef _MSC_VER
    unsigned long index;
    _BitScanForward(&index, n);
    return index;
#else
    return __builtin_ctz(n);
#endif
}

}  // namespace internal

}  // namespace atcoder

#endif  // ATCODER_INTERNAL_BITOP_HPP

#ifndef ATCODER_SEGTREE_HPP
#define ATCODER_SEGTREE_HPP 1

namespace atcoder {

template <class S, S (*op)(S, S), S (*e)()>
struct segtree {
   public:
    segtree() : segtree(0) {}
    segtree(int n) : segtree(std::vector<S>(n, e())) {}
    segtree(const std::vector<S>& v) : _n(int(v.size())) {
        log = internal::ceil_pow2(_n);
        size = 1 << log;
        d = std::vector<S>(2 * size, e());
        for (int i = 0; i < _n; i++) d[size + i] = v[i];
        for (int i = size - 1; i >= 1; i--) {
            update(i);
        }
    }

    void set(int p, S x) {
        assert(0 <= p && p < _n);
        p += size;
        d[p] = x;
        for (int i = 1; i <= log; i++) update(p >> i);
    }

    S get(int p) {
        assert(0 <= p && p < _n);
        return d[p + size];
    }

    S prod(int l, int r) {
        assert(0 <= l && l <= r && r <= _n);
        S sml = e(), smr = e();
        l += size;
        r += size;

        while (l < r) {
            if (l & 1) sml = op(sml, d[l++]);
            if (r & 1) smr = op(d[--r], smr);
            l >>= 1;
            r >>= 1;
        }
        return op(sml, smr);
    }

    S all_prod() { return d[1]; }

    template <bool (*f)(S)>
    int max_right(int l) {
        return max_right(l, [](S x) { return f(x); });
    }
    template <class F>
    int max_right(int l, F f) {
        assert(0 <= l && l <= _n);
        assert(f(e()));
        if (l == _n) return _n;
        l += size;
        S sm = e();
        do {
            while (l % 2 == 0) l >>= 1;
            if (!f(op(sm, d[l]))) {
                while (l < size) {
                    l = (2 * l);
                    if (f(op(sm, d[l]))) {
                        sm = op(sm, d[l]);
                        l++;
                    }
                }
                return l - size;
            }
            sm = op(sm, d[l]);
            l++;
        } while ((l & -l) != l);
        return _n;
    }

    template <bool (*f)(S)>
    int min_left(int r) {
        return min_left(r, [](S x) { return f(x); });
    }
    template <class F>
    int min_left(int r, F f) {
        assert(0 <= r && r <= _n);
        assert(f(e()));
        if (r == 0) return 0;
        r += size;
        S sm = e();
        do {
            r--;
            while (r > 1 && (r % 2)) r >>= 1;
            if (!f(op(d[r], sm))) {
                while (r < size) {
                    r = (2 * r + 1);
                    if (f(op(d[r], sm))) {
                        sm = op(d[r], sm);
                        r--;
                    }
                }
                return r + 1 - size;
            }
            sm = op(d[r], sm);
        } while ((r & -r) != r);
        return 0;
    }

   private:
    int _n, size, log;
    std::vector<S> d;

    void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
};

}  // namespace atcoder

#endif  // ATCODER_SEGTREE_HPP

using namespace atcoder;

struct monoid {
    int val, idx;

    static monoid op(monoid lhs, monoid rhs) {
        return lhs.val < rhs.val ? lhs : rhs;
    }

    static monoid e() { return {mod, -1}; }
};

struct seg {
    int val, idx, l, r;
};

int main() {
    int n;
    scanf("%d", &n);
    vector<vector<monoid>> a(2, vector<monoid>(n, {mod, -1}));
    rep(i, n) {
        scanf("%d", &a[i % 2][i].val);
        a[i % 2][i].idx = i;
    }
    segtree<monoid, monoid::op, monoid::e> st0(a[0]), st1(a[1]);

    auto cmp = [](const seg& s1, const seg& s2) { return s1.val > s2.val; };
    priority_queue<seg, vector<seg>, decltype(cmp)> que(cmp);
    auto get_min = [&](int l, int r) {
        return l % 2 == 0 ? st0.prod(l, r) : st1.prod(l, r);
    };
    auto mo = st0.all_prod();
    que.push({mo.val, mo.idx, 0, n});

    vector<int> ans;
    while (!que.empty()) {
        auto s = que.top();
        que.pop();
        ans.push_back(s.val);
        auto [w, j] = get_min(s.idx + 1, s.r);
        ans.push_back(w);
        if (s.idx - s.l) {
            mo = get_min(s.l, s.idx);
            que.push({mo.val, mo.idx, s.l, s.idx});
        }
        if (j - s.idx - 1) {
            mo = get_min(s.idx + 1, j);
            que.push({mo.val, mo.idx, s.idx + 1, j});
        }
        if (s.r - j - 1) {
            mo = get_min(j + 1, s.r);
            que.push({mo.val, mo.idx, j + 1, s.r});
        }
    }
    for (auto i : ans) printf("%d ", i);
    printf("\n");
}

Measured memory_bytes: 17000