#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp> 
#include <ext/pb_ds/detail/standard_policies.hpp>
using namespace __gnu_pbds;
using namespace std;
#define getbit(n, i) (((n) & (1LL << (i))) != 0) 
#define setbit0(n, i) ((n) & (~(1LL << (i)))) 
#define setbit1(n, i) ((n) | (1LL << (i))) 
#define togglebit(n, i) ((n) ^ (1LL << (i))) 
#define lastone(n) ((n) & (-(n))) 
char gap = 32;
#define int long long
#define ll long long 
#define lll __int128_t
#define pb push_back
#define pii pair<int,int>
typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll hashPrime = 1610612741;

const int N = 1120;
int ara[N];
pii target[N];
int cur[N];
void solve(){
    int n;
    cin >> n;
    n = 1<<n;
    for (int i=0; i<n; i++) cin >> ara[i];
    for(int i=0;i<n;i++)    target[i] = {ara[i], i};
    sort(target, target+n);
    for(int i=0;i<n;i++)    cur[i] = target[i].second;
    vector<pii> res;
    for (int i=n-1; i>=0; i--) {
        //if (ara[i] == target[i].first) continue;
        int pos = cur[i];
        int mul = 1;
        for(int b=0;b<10;b++){
            if( mul & pos ){
                res.pb({pos, pos^mul});
                //cout<<pos<<" "<<(pos^mul)<<endl;
                swap(cur[pos], cur[pos^mul]);
                
                pos ^= mul;
            }
            mul = mul<<1;
        }
        pos = 0;
        mul = 1;
        for(int b=0;b<10;b++){
            if( mul & i ){
                res.pb({pos, pos^mul});
               // cout<<pos<<" "<<(pos^mul)<<endl;
                swap(cur[pos], cur[pos^mul]);
                pos ^= mul;
            }
            mul <<= 1;
        }


    }
    cout<<res.size()<<endl;
    for(auto p: res) cout << p.first << " " << p.second << endl;

}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
     solve();
    
    return 0;
}