TASKC

#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
using ll = long long;
using pii = pair<int, int>;

constexpr int N = 3e5+5;

int n, mp[N], pm[N], el;
vector<pii> ans;

void sw2(int i, int j)
{
  ans.push_back({i, j});
  swap(pm[mp[i]], pm[mp[j]]);
  swap(mp[i], mp[j]);
}

void sw1(int id)
{
  int i = 1, temp;
  if (id<n/2)
   i = n;
  sw2(i, id);
}


void Solve()
{
  cin >> n;
  for (int i = 1; i <= n; i++)
  {
    cin >> el;
    mp[i] = el;
    pm[el] = i;
  }
  int id1 = n/4+1, id2 = n - n/4;
  for (int i = id1; i < id2; i++)
  {
    if (pm[i]!=i)
    {
      if (abs(pm[i]-i)<n/2)
        sw1(pm[i]);
      sw2(pm[i], i);
    }
  }
  for (int i = 1; i < id1; i++)
  {
    if (pm[i]!=i)
    {
      if (abs(pm[i]-i)<n/2)
      {
        sw1(pm[i]);
      }
      sw2(pm[i], i);
    }
  }
  for (int i = id2; i <= n; i++)
  {
    if (pm[i]!=i)
    {
      if (abs(pm[i]-i)<n/2)
      {
        sw1(pm[i]);
      }
      sw2(pm[i], i);
    }
  }
  cout << ans.size() << endl;
  for (auto [a, b]:ans)
  {
    cout << a << " " << b << endl;
  }
}

int main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  Solve();
  return 0;
}