#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define maxn 10005
#define put() putchar('\n')
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
using namespace std;
Tp void read(T &x){
    int f=1;x=0;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    x*=f;
}
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
#define fi first
#define se second
#define mk make_pair
const int mod=1e9+7;
int power(int x,int y=mod-2) {
	int sum=1;
	while (y) {
		if (y&1) sum=sum*x%mod;
		x=x*x%mod;y>>=1;
	}
	return sum;
}
int n,a[maxn],N;
pair<int,int>ans[100005];
int cnt,id[maxn],rk[maxn],c[maxn];
bool cmp(int x,int y) {return a[x]<a[y];}
void move(int x,int y) {swap(a[x],a[y]),swap(rk[x],rk[y]),ans[++cnt]=mk(x,y);}
void solve(int l,int r,int d) {
	if (l==r) return ;
//	gdb(l,r,d);
	int mid=l+r>>1,tot=0,i;
	for (i=l;i<=mid;i++) if ((rk[i]>>d)%2) c[++tot]=i;
	for (i=mid+1;i<=r;i++) if ((rk[i]>>d)%2==0) move(i,c[tot--]);
	assert(tot==0);
	solve(l,mid,d-1);
	solve(mid+1,r,d-1);
}
signed main(void){
	int i;
	read(n);N=(1<<n);
	for (i=0;i<N;i++) read(a[i]),id[i]=i;
	sort(id,id+N,cmp);
	for (i=0;i<N;i++) rk[id[i]]=i;
	solve(0,N-1,n-1);
	for (i=0;i<N;i++) assert(rk[i]==i);
	printf("%d\n",cnt);
	for (i=1;i<=cnt;i++) printf("%d %d\n",ans[i].fi,ans[i].se);
	return 0;
}