#include <bits/stdc++.h>
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin>>n;
    vector<int>a(n);
    map<int,int>b;
    for(int i=0; i<n; i++){
        cin>>a[i]; b[a[i]]=a[i];}
    vector<int>ans;
    for(int i=0; i<n/2; i++){
        int p=a[i], q=a[n-i-1];
        while(p!=b[p]){p=b[p];}
        while(q!=b[q]){q=b[q];}
        int p2=a[i], q2=a[n-i-1];
        while(p2!=b[p2]){int t=p2; p2=b[p2]; b[t]=p;}
        while(q2!=b[q2]){int t=q2; q2=b[q2]; b[t]=q;}
        if(p==q)continue;
        int x=min(p,q);
        int y=max(p,q);
        ans.push_back(y);
        ans.push_back(x);
        b[y]=x;}
    cout<<ans.size()/2<<'\n';
    for(int i=0; i<ans.size(); i+=2)
        cout<<ans[i]<<" "<<ans[i+1]<<'\n';
    return 0;
}