#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
using namespace std;

int main()
{
    int n;
    cin>>n;

    int proverka=n-1;

    vector<pair<int, int>>v;
    for(int i=0; i<n; i++){
        int a;
        cin>>a;
        v.push_back(make_pair(a,i));
    }
   sort(v.begin(), v.end());




    vector<pair<int, int>>v_;

    int counter=0;
    for(int x = 0; x <v.size(); x++ ){
        bool ok = false;
        for(int i=v.size()-1; i>=0; i--){
            
            if(v[i].first<=0){
                continue;
            }
            for(int j=0; j<n; j++){
                if(i != j){
                    
                    if(v[i].first<=0){
                        continue;
                    }
                    
                    if(v[j].first<=0){
                        continue;
                    }
                    
                    v[i].first--;
                    v[j].first--;
                    
                    counter++;
                    
                    v_.push_back(make_pair(v[i].second+1, v[j].second+1));
                    ok = true;
                    break;
                }
            }
            if(ok) {
                break;
            }
        }
        sort(v.begin(), v.end());

    }
        if(counter<n){
            for(int i=0; i<v_.size(); i++){
                    cout<<v_[i].first<<" "<<v_[i].second<<endl;
            }
        }
    
    else{
        cout<<"PROBLEM";
    }






    return 0;
}