#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<pair<int,int>> A(2*N);
    for(int i=0; i<2*N; i++){
        int a; cin >> a;
        A.at(i) = {a,i};
    }
    sort(A.begin(),A.end());
    vector<pair<int,int>> X;
    long long answer = 0;
    for(int i=0; i<N; i++){
        auto [a1,p1] = A.at(i);
        auto [a2,p2] = A.at(2*N-1-i);
        answer += abs(a2-a1),X.push_back({p1,p2});
    }
    cout << answer << "\n";
    for(auto [a,b] : X) cout << a+1 << " " << b+1 << "\n";
}