#include <algorithm>
#include <vector>
#include <cstdio>

#define maxn 5000

using namespace std;

int n;
vector< int > deg[maxn];
vector< pair< int, int > > tmp;

void load() {
   scanf( "%d", &n );
   for( int i = 0; i < n; ++i ) {
      int t;
      scanf( "%d", &t );
      deg[t].push_back( i );
   }
}

void spoji( int i ) {
   int a = deg[i].back(), ii = i;
   deg[i].pop_back();

   for( int j = 0; j < ii; ++j ) {
      for(; deg[i].empty(); --i );

      printf( "%d %d\n", a+1, deg[i].back()+1 );
      if( i ) tmp.push_back( make_pair( i-1, deg[i].back() ) );
      deg[i].pop_back();
   }

   while( tmp.size() ) {
      deg[ tmp.back().first ].push_back( tmp.back().second );
      tmp.pop_back();
   }
}

int main(void) {
   load();

   for( int i = n-1; i >= 0; --i )
      for( ; !deg[i].empty(); spoji( i ) );

   return 0;
}