description: An important meeting is to be held and there are exactly n people invited. At any moment, any two people can step back and talk in private. The same two people can talk several (as many as they want) times per meeting.
  
  Each person has limited sociability. The sociability of the i-th person is a non-negative integer a_i. This means that after exactly a_i talks this person leaves the meeting (and does not talk to anyone else anymore). If a_i = 0, the i-th person leaves the meeting immediately after it starts.
  
  A meeting is considered most productive if the maximum possible number of talks took place during it.
  
  You are given an array of sociability a, determine which people should talk to each other so that the total number of talks is as large as possible.
  
  Input
  
  The first line contains an integer t (1 ≤ t ≤ 1000) — the number of test cases.
  
  The next 2t lines contain descriptions of the test cases.
  
  The first line of each test case description contains an integer n (2 ≤ n ≤ 2 ⋅ 10^5) —the number of people in the meeting. The second line consists of n space-separated integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ 2 ⋅ 10^5) — the sociability parameters of all people. 
  
  It is guaranteed that the sum of n over all test cases does not exceed 2 ⋅ 10^5. It is also guaranteed that the sum of all a_i (over all test cases and all i) does not exceed 2 ⋅ 10^5.
  
  Output
  
  Print t answers to all test cases.
  
  On the first line of each answer print the number k — the maximum number of talks possible in a meeting.
  
  On each of the next k lines print two integers i and j (1 ≤ i, j ≤ n and i ≠ j) — the numbers of people who will have another talk.
  
  If there are several possible answers, you may print any of them.
  
  Example
  
  Input
  
  
  8
  2
  2 3
  3
  1 2 3
  4
  1 2 3 4
  3
  0 0 2
  2
  6 2
  3
  0 0 2
  5
  8 2 0 1 1
  5
  0 1 0 0 6
  
  
  Output
  
  
  2
  1 2
  1 2
  3
  1 3
  2 3
  2 3
  5
  1 3
  2 4
  2 4
  3 4
  3 4
  0
  2
  1 2
  1 2
  0
  4
  1 2
  1 5
  1 4
  1 2
  1
  5 2
solution: #!/usr/bin/env python3
  import sys
  import getpass  # not available on codechef
  import math, random
  import functools, itertools, collections, heapq, bisect
  from collections import Counter, defaultdict, deque
  input = sys.stdin.readline  # to read input quickly
  
  # available on Google, AtCoder Python3, not available on Codeforces
  # import numpy as np
  # import scipy
  
  M9 = 10**9 + 7  # 998244353
  yes, no = "YES", "NO"
  # d4 = [(1,0),(0,1),(-1,0),(0,-1)]
  # d8 = [(1,0),(1,1),(0,1),(-1,1),(-1,0),(-1,-1),(0,-1),(1,-1)]
  # d6 = [(2,0),(1,1),(-1,1),(-2,0),(-1,-1),(1,-1)]  # hexagonal layout
  MAXINT = sys.maxsize
  
  # if testing locally, print to terminal with a different color
  OFFLINE_TEST = getpass.getuser() == "hkmac"
  # OFFLINE_TEST = False  # codechef does not allow getpass
  def log(*args):
      if OFFLINE_TEST:
          print('\033[36m', *args, '\033[0m', file=sys.stderr)
  
  def solve(*args):
      # screen input
      if OFFLINE_TEST:
          log("----- solving ------")
          log(*args)
          log("----- ------- ------")
      return solve_(*args)
  
  def read_matrix(rows):
      return [list(map(int,input().split())) for _ in range(rows)]
  
  def read_strings(rows):
      return [input().strip() for _ in range(rows)]
  
  def minus_one(arr):
      return [x-1 for x in arr]
  
  def minus_one_matrix(mrr):
      return [[x-1 for x in row] for row in mrr]
  
  # ---------------------------- template ends here ----------------------------
  
  
  def solve_(arr):
      # your solution here
  
      arr = [(-x,i) for i,x in enumerate(arr) if x > 0]
      arr.sort()
      res = []
  
      while len(arr) > 1:
  
          (x,i) = heapq.heappop(arr)
          (y,j) = heapq.heappop(arr)
  
          x += 1
          y += 1
  
          if x < 0:
              heapq.heappush(arr, (x,i))
          if y < 0:
              heapq.heappush(arr, (y,j))
  
          res.append(f"{i+1} {j+1}")
  
      return res
  
  
  # for case_num in [0]:  # no loop over test case
  # for case_num in range(100):  # if the number of test cases is specified
  for case_num in range(int(input())):
  
      # read line as an integer
      k = int(input())
  
      # read line as a string
      # srr = input().strip()
  
      # read one line and parse each word as a string
      # lst = input().split()
  
      # read one line and parse each word as an integer
      # a,b,c = list(map(int,input().split()))
      arr = list(map(int,input().split()))
      # lst = minus_one(lst)
  
      # read multiple rows
      # arr = read_strings(k)  # and return as a list of str
      # mrr = read_matrix(k)  # and return as a list of list of int
      # mrr = minus_one_matrix(mrr)
  
      res = solve(arr)  # include input here
  
      # print length if applicable
      print(len(res))
  
      # parse result
      # res = " ".join(str(x) for x in res)
      res = "\n".join(str(x) for x in res)
      # res = "\n".join(" ".join(str(x) for x in row) for row in res)
  
      # print result
      # print("Case #{}: {}".format(case_num+1, res))   # Google and Facebook - case number required
  
      print(res)
  