#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;

int main(){
   ll n; cin >> n;
   vector<pair<ll,ll>>a(2*n);
   for(ll i=0; i < n*2;i++){
    cin >> a[i].first;
    a[i].second=i+1;
   }
   sort(a.begin(),a.end());
   ll c=0;
   for(ll i=0; i < n;i++){
    c += abs(a[2*n-i-1].first-a[i].first);
   }
   cout << c << endl;
   for(ll i=0; i < n;i++){
    cout << a[i].second << " " << a[2*n-i-1].second << endl;
   }
}