#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef double db;

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int n;
	cin >> n;
	
	VI p(1 << n);
	FOR (i, 0, SZ(p))
		cin >> p[i];
	
	vector<PII> ans;
	FOR (bt, 0, n)
	{
		FOR (mask, 0, 1 << n)
		{
			if ((mask & bt) & 1) continue;
			int i = mask;
			int j = mask | (1 << bt);
			if (p[i] > p[j])
			{
				swap(p[i], p[j]);
				ans.PB({i, j});
			} 
		}
	}
	cout << SZ(ans) << '\n';
	for (auto [i, j] : ans)
		cout << i << ' ' << j << '\n';
	
	
	return 0;
}