//#define _GLIBCXX_DEBUG

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

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++){cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++){for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>vector<vector<T>>vec(ll x, ll y, T w){vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v(ts...))>(a,make_v(ts...));}
template<typename T1, typename T2>ostream &operator<<(ostream &os, const pair<T1, T2>&p){return os << p.first << " " << p.second;}
template<typename T>ostream &operator<<(ostream &os, const vector<T> &v){for(auto &z:v)os << z << " ";cout<<"|"; return os;}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll n;cin>>n;
  vector<ll>d(n);
  rep(i,0,n){
    cin>>d[i];
  }
  vector<ll>ord(n);
  iota(ALL(ord),0);
  map<ll,ll>mp;
  sort(ALL(ord),[&](ll x,ll y){
    return d[x]>d[y];
  });
  rep(i,0,n)mp[d[i]]=i;
  vector<ll>sub(n,1);
  vector<P>ret;
  ll root=-1;
  for(auto i:ord){
    if(sub[i]==n){
      root=i;
      break;
    }
    ll k=d[i]-(n-2*sub[i]);
    if(mp.count(k)){
      sub[mp[k]]+=sub[i];
      ret.EB(i,mp[k]);
    }
    else{
      judge=false;
      break;
    }
  }
  //debug(sub,n);
  //debug(ret,ret.size());
  if(root==-1)judge=false;
  else{
    ll sum=0;
    vector<vector<ll>>g(n);
    for(auto p:ret){
      g[p.fi].PB(p.se);
      g[p.se].PB(p.fi);
    }
    auto dfs=[&](auto &&f,ll k,ll par,ll d)->void{
      for(auto to:g[k]){
        if(to==par)continue;
        f(f,to,k,d+1);
      }
      sum+=d;
    };
    dfs(dfs,root,-1,0);
    if(sum!=d[root])judge=false;
  }
  if(judge){
    for(auto z:ret)cout<<z.fi+1 spa z.se+1<<endl;
  }
  else cout<<-1<<endl;
  return 0;
}

Measured memory_bytes: 22832