#include<bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define endl "\n"
using namespace std;

const int N = 1e5 + 10, T = 100;

int a[N], deg[N], rev_idx[N], cost[N];

int n;

int st[N / T], ed[N / T];

vector<int> rrh[N / T];

struct IT {

int lazy[T * 4];

pair<int, int> T[T * 4];


void build(int s, int l, int r) {
  if (l == r) {
    T[s] = make_pair(0, l);
    return;
  }
  int mid = l + r >> 1;
  build(s << 1, l, mid);
  build(s << 1 | 1, mid + 1, r);
  T[s] = min(T[s << 1], T[s << 1 | 1]);
}

void push(int s, int l, int r) {
  if (!lazy[s]) return;
  T[s].first += lazy[s];
  if (l != r) {
    lazy[s << 1] += lazy[s];
    lazy[s << 1 | 1] += lazy[s];
  }
  lazy[s] = 0;
}

void up(int s, int l, int r, int from, int to, int val) {
  push(s, l, r);
  if (l > to || r < from) return;
  if (from <= l && r <= to) {
    lazy[s] = val;
    push(s, l, r);
    return;
  }
  int mid = l + r >> 1;
  up(s << 1, l, mid, from, to, val);
  up(s << 1 | 1, mid + 1, r, from, to, val);
  T[s] = min(T[s << 1], T[s << 1 | 1]);
}

} it[N / T];

int bit[N];

void add (int pos, int val) {
  while (pos) {
    bit[pos] += val;
    pos -= pos & -pos;
  }
}

int get(int pos) {
  int ret = 0;
  while (pos <= n) {
    ret += bit[pos];
    pos += pos & -pos;
  }
  return ret;
}

vector<int> q[2];

int32_t main() {
  #define task ""

  cin.tie(0) -> sync_with_stdio(0);

  if (fopen("task.inp", "r")) {
    freopen("task.inp", "r", stdin);
    freopen("task.out", "w", stdout);
  }

  if (fopen(task".inp", "r")) {
    freopen (task".inp", "r", stdin);
    freopen (task".out", "w", stdout);
  }

  cin >> n;

  for(int i = 1; i <= n; i++) cin >> a[i];

  for(int i = 1; i <= n; i++) rev_idx[a[i]] = i;

  for(int i = 1; i <= n; i++) {
    cost[i] = get(a[i]);
    add(a[i], 1);
  }

  for(int i = n, mn = 1e9; i >= 1; i--) {
    deg[i] = a[i] > mn;
    mn = min(mn, a[i]);
  }

  auto idx = [&] (int block, int val) {
    return upper_bound(all(rrh[block]), val) - rrh[block].begin();
  };

  auto handle = [&] (int block) {
    while (it[block].T[1].first == 0) {
      int x = it[block].T[1].second;
      it[block].up(1, 1, ed[block] - st[block] + 1, x, x, 1e9);
      int y = rev_idx[x];
      q[deg[y]].push_back(y);
    }
  };

  for(int block = 0; block <= n / T; block++) {
    st[block] = max(1, block * T);
    ed[block] = min(n, block * T + T - 1);
    for(int i = st[block]; i <= ed[block]; i++) rrh[block].push_back(a[i]);
    sort(all(rrh[block]));
    rrh[block].resize(unique(all(rrh[block])) - rrh[block].begin());
    it[block].build(1, 1, ed[block] - st[block] + 1);
    for(int i = st[block]; i <= ed[block]; i++) {
      int pos = idx(block, a[i]);
      it[block].up(1, 1, ed[block] - st[block] + 1, pos, pos, cost[i]);
    }
    handle(block);
  }

  auto del = [&] (int i) {
    int group = i / T;
    for(int j = i + 1; j <= ed[group]; j++) if (a[i] > a[j]) {
      int pos = idx(group, a[j]);
      it[group].up(1, 1, ed[group] - st[group] + 1, pos, pos, -1);
    }
//    exit(0);
    handle(group);
    for(int block = group + 1; block <= n / T; block++) {
      int pos = idx(block, a[i]);
      if (!pos) continue;
      it[block].up(1, 1, ed[block] - st[block] + 1, 1, pos, -1);
      handle(group);
    }
  };

  vector<pair<int, int> > ans;

//  del(1);
//  cout << q[0].size() << endl;
//  for(int &j : q[1]) cout << j << " "; cout << endl;
//  exit(0);

  while (1) {
    if (q[1].size() >= 2) {
      int x = q[1].back(); q[1].pop_back();
      int y = q[1].back(); q[1].pop_back();
      ans.emplace_back(a[x], a[y]);
      del(x);
      del(y);
    }
    else if (q[1].size() == 1) {
      int x = q[1].back(); q[1].pop_back();
      if (q[0].empty()) ans.emplace_back(a[x], a[x]);
      else {
        int y = q[0].back(); q[0].pop_back();
        ans.emplace_back(a[x], a[y]);
      }
      del(x);
    }
    else {
      if (q[0].empty()) break;
      int x = q[0].back(); q[0].pop_back();
      if (q[0].empty()) {
        ans.emplace_back(a[x], a[x]);
        break;
      }
      int y = q[0].back(); q[0].pop_back();
      ans.emplace_back(a[x], a[y]);
    }
  }

  cout << ans.size() << endl;

  for(auto &[x, y] : ans) cout << x << " " << y << endl;
}

answer.code:20:16: error: declaration of ‘std::pair<int, int> IT::T [400]’ changes meaning of ‘T’ [-Wchanges-meaning]
   20 | pair<int, int> T[T * 4];
      |                ^
answer.code:20:18: note: used here to mean ‘const int T’
   20 | pair<int, int> T[T * 4];
      |                  ^
answer.code:6:25: note: declared here
    6 | const int N = 1e5 + 10, T = 100;
      |                         ^
answer.code: In function ‘int32_t main()’:
answer.code:86:12: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   86 |     freopen("task.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
answer.code:87:12: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   87 |     freopen("task.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
answer.code:91:13: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   91 |     freopen (task".inp", "r", stdin);
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
answer.code:92:13: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   92 |     freopen (task".out", "w", stdout);
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~