#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) (x).begin(), (x).end()
#ifdef LOCAL
#define debug(...) __VA_ARGS__;
#else
#define debug(...) 24;
#endif

template<class A, class B>
ostream& operator<<(ostream &os, pair<A, B> &p);
template<class T>
ostream& operator<<(ostream &os, vector<T> &v);
template<class T, size_t sz>
ostream& operator<<(ostream &os, array<T, sz> &v);

template<class A, class B>
ostream& operator<<(ostream &os, pair<A, B> &p) {
  return os << '(' << p.first << ',' << p.second << ')';
}

template<class T>
ostream& operator<<(ostream &os, vector<T> &v) {
  os << '{';
  bool f = 0; for(auto &i : v) { if(f) os << ',';os << i; f = 1;}
  return os << '}';
}

template<class T, size_t sz>
ostream& operator<<(ostream &os, array<T, sz> &v) {
  os << '{';
  bool f = 0; for(auto &i : v) { if(f) os << ',';os << i; f = 1;}
  return os << '}';
}

int main() {
  ios::sync_with_stdio(0); cin.tie(0);
  int n; cin >> n;
  int sz = 1<<n;
  vector<int> a(sz);
  for(int &i : a) cin >> i;
  vector<pair<int, int>> ans;
  for(int to = 0; to < sz; to++) {
    int mn = 1e9, from = sz;
    for(int i = to; i < sz; i++) {
      if(mn > a[i]) {
        mn = a[i];
        from = i;
      }
    }
    debug(cerr << "from = " << from << " to = " << to << '\n');
    for(int i = n-1; i >= 0; i--) {
      int bit = 1<<i;
      if((~from&bit) && (to&bit)) {
        debug(cerr << from << ' ' << (from | bit) << '\n');
        swap(a[from], a[from|bit]);
        ans.emplace_back(from, (from|bit));
        from |= bit;
      }
    }
    for(int i = n-1; i >= 0; i--) {
      int bit = 1<<i;
      if((from&bit) && (~to&bit)) {
        debug(cerr << from << ' ' << (from ^ bit) << '\n');
        swap(a[from], a[from^bit]);
        ans.emplace_back(from, (from^bit));
        from ^= bit;
      }
    }
    debug(cerr << a << '\n');
  }
  cout << ans.size() << '\n';
  for(auto [x, y] : ans)
    cout << x << ' ' << y << '\n';
}