#include <bits/stdc++.h>   int main() {     int n;     scanf( %d , &n);     std::vector<std::pair<int, int> > a(n + 1);     for (int p = 0; p < n; p++) {       int x;       scanf( %d , &x);       a[p] = std::make_pair(x, p + 1);     }     sort(++a.begin(), a.end(), std::greater<std::pair<int, int> >());     int ind(0);     std::vector<std::pair<int, int> > comm;     for (int p = 0; p < n; p++) {       for (int q = ind + 1; q <= ind + a[p].first; q++) {         if (q >= n) {           break;         }         comm.push_back(std::make_pair(a[p].second, a[q].second));       }       ind += a[p].first;       if (ind <= p) {         break;       }     }     if (comm.size() < n - 1) {       puts( -1 );     } else {       printf( %d n , n - 1);       for (int p = 0; p < comm.size(); p++) {         printf( %d %d n , comm[p].first, comm[p].second);       }     }     return 0;   }   