///jai sri krishna
///jai maa kali


#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace __gnu_pbds;


typedef long long ll;
typedef long double ld;
typedef tree<
ll,
null_type,
less_equal<ll>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

#define db double
#define pii pair< pair<ll,ll>, ll >
#define f(i,a,b) for(ll i=a;i<b;i++)
#define fi(i,a,b,c) for(ll i=a;i<b;i+=c)
#define fr(i,a,b) for(ll i=a;i>=b;i--)
#define fri(i,a,b,c) for(ll i=a;i>=b;i-=c)
#define pb push_back
#define ss second
#define ff first
#define in insert
#define sq(x)  (x*x)
#define all(a)  a.begin(),a.end()
#define nl "\n"
#define mnpq  priority_queue <pii, vector<pii>, greater<pii> >

ll gcd(ll a,ll b){
       if(b==0)return a;
       return gcd(b,a%b);
}
int getRandom(int L,int R)
{
    return rng()%(R-L+1) + L;
}

ll lcm(ll a,ll b){
       return ((a)/gcd(a,b))*b;
}

ll bigmod(ll a,ll n,ll md){
       if(n==0){
           return 1;
       }
       if(n==1){
           return a%md;
       }
       ll d= bigmod(a,n/2,md);
       if(n%2==0){
           return (d*d)%md;
       }
       else{
           return ( ((d*d)%md) * (a%md) )%md;
       }
}

bool sortbysec(const pair<int,int> &a,
            const pair<int,int> &b)
{

    if(a.first==b.first){
         return (a.second > b.second);
    }

    return (a.first< b.first);
}


const ll  N = 103000;
const ll mod = 998244353;

const ll neginf= -1e18;
const ll inf = 1e9;
const ld eps= 1e-9;

/// Solve part by part
/// Think small case
/// Think reverse order


/// test against atleast 10 cases

/// give 10 min before submission
/// wrong submission 20 min penalty


/// use binary search for maximum minimum problem
/// use broute force to check test case in another solution




ll cal(ll n){

   ll f=1;

   f(i,1,n+1)f=f*2;

   return f;
}

bool pos(ll i,ll j){

   if(i<j)swap(i,j);

   ll df=0;
    while(i>0){
        ll d=i%2;
        ll e=j%2;
        i/=2;
        j/=2;
        if(d!=e)df++;
        if(df>1)break;
    }

    return df==1;

}

vector<ll>v[N];
ll vis[N];
ll dis[N];
ll par[N];

set<ll>upd;

void bfs(ll d,ll chi){

    vis[d]=1;

    queue<ll>q;
    par[d]=-1;

    dis[d]=0;


    upd.in(d);


    ll pr=d;

    ll hoi=0;

    q.push(d);

    while(!q.empty()){

         if(hoi==1)break;

         ll d=q.front();
         q.pop();
         for(ll ch:v[d]){
              if(vis[ch]==0){
                  vis[ch]=1;

                 //cout<<"make vis "<<ch<<endl;
                  q.push(ch);
                  par[ch]=d;
                  //cout<<ch<<endl;

                  upd.in(ch);

                  if(ch==chi){

                     hoi=1;
                     break;
                  }
              }
         }
    }

}

int main(){

       ios_base::sync_with_stdio(false);
       cin.tie(NULL);
       cout.tie(NULL);

       ll n;
       cin>>n;
       ll m=cal(n);
       ll a[m];
       ll b[m];

       map<ll,ll>mp;

       f(i,0,m){
         cin>>a[i];
         mp[a[i]]=i;
         b[i]=a[i];
       }
       sort(b,b+m);

       f(i,0,m){
         f(j,i+1,m){
             if(pos(i,j)){
                  v[i].pb(j);
                  v[j].pb(i);
             }
         }
       }



        vector<pair<ll,ll>>ans;


        ll bd=0;
        while(1){


        ll cd=0;
       f(i,0,m){

          if(a[i]==b[i])continue;

          ///swap

          ll chi=mp[b[i]]; ///chi= amar samner kake chai tar pos

         // cout<<"Chi "<<chi<<endl;

          bfs(i,chi);  ///i= amar position

         // cout<<i<<" "<<chi<<endl;

          ll nd=chi;

        //  cout<<vis[nd]<<endl;

          vector<ll>vv;

          ll mn=i;
          while(nd!=-1){

               /// cout<<nd<<endl;
                vv.pb(nd);
                mn=min(mn,nd);
                nd=par[nd];

          }

          if(vv.size()>2){
                 for(ll x:upd){
                      vis[x]=0;
                      dis[x]=0;
                      par[x]=0;
                  }
                   upd.clear();

            continue;
          }

          cd=1;


          f(i,0,vv.size()-1){
             swap(a[vv[i]],a[vv[i+1]]);

             mp[a[vv[i]]]=vv[i];
             mp[a[vv[i+1]]]=vv[i+1];

             ans.pb({vv[i],vv[i+1]});
          }
          ///chi theke amar position e asci

          if(mn<i){///ami lower pos er value use korci
             ll sp=0;
             f(j,1,vv.size()){
                if(vv[j]==mn){
                     sp=vv[j-1];
                     break;
                }
             }

             swap(a[mn],a[sp]);

             ans.pb({mn,sp});
             mp[a[mn]]=mn;
             mp[a[sp]]=sp;



          }

          for(ll x:upd){
             vis[x]=0;
             dis[x]=0;
             par[x]=0;
          }
          upd.clear();

       }

       if(cd==0)break;

        }


       f(i,0,m){

          if(a[i]==b[i])continue;

          ///swap

          ll chi=mp[b[i]]; ///chi= amar samner kake chai tar pos

         // cout<<"Chi "<<chi<<endl;

          bfs(i,chi);  ///i= amar position

         // cout<<i<<" "<<chi<<endl;

          ll nd=chi;

        //  cout<<vis[nd]<<endl;

          vector<ll>vv;

          ll mn=i;
          while(nd!=-1){

               /// cout<<nd<<endl;
                vv.pb(nd);
                mn=min(mn,nd);
                nd=par[nd];

          }


          f(i,0,vv.size()-1){
             swap(a[vv[i]],a[vv[i+1]]);

             mp[a[vv[i]]]=vv[i];
             mp[a[vv[i+1]]]=vv[i+1];

             ans.pb({vv[i],vv[i+1]});
          }
          ///chi theke amar position e asci

          if(mn<i){///ami lower pos er value use korci
             ll sp=0;
             f(j,1,vv.size()){
                if(vv[j]==mn){
                     sp=vv[j-1];
                     break;
                }
             }

             swap(a[mn],a[sp]);

             ans.pb({mn,sp});
             mp[a[mn]]=mn;
             mp[a[sp]]=sp;



          }

          for(ll x:upd){
             vis[x]=0;
             dis[x]=0;
             par[x]=0;
          }
          upd.clear();

       }






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

       f(i,0,ans.size()){
        ll ft=min(ans[i].ff,ans[i].ss);
        ll st=max(ans[i].ff,ans[i].ss);
          cout<<ft<<" "<<st<<nl;
       }






}