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