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: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.*;
  public class Main{
      static class FastScanner {
              BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
              StringTokenizer st = new StringTokenizer("");
  
              String next() {
                  while (!st.hasMoreTokens())
                      try {
                          st = new StringTokenizer(br.readLine());
                      } catch (IOException e) {
                          e.printStackTrace();
                      }
                  return st.nextToken();
              }
  
              int nextInt() {
                  return Integer.parseInt(next());
              }
  
              int[] nextArray(int n) {
                  int[] a = new int[n];
                  for (int i = 0; i < n; i++) a[i] = nextInt();
                  return a;
              }
              long[] nextArray(long n) {
                  long[] a = new long[(int) n];
                  for (int i = 0; i < n; i++) a[i] = nextLong();
                  return a;
              }
  
              long nextLong() {
                  return Long.parseLong(next());
              }
          }
      static class FastWriter extends PrintWriter {
              FastWriter(){
                  super(System.out);
              }
              void println(int[] array) {
                  for(int i=0; i<array.length; i++) {
                      print(array[i]+" ");
                  }
                  println();
              }
              void println(long [] array) {
                  for(int i=0; i<array.length; i++) {
                      print(array[i]+" ");
                  }
                  println();
              }
          }
      static int MOD=1000003;
      public static void main(String[] args) {
          FastScanner in = new FastScanner();
          FastWriter out = new FastWriter();
          int t=1;
          t=in.nextInt();
          while (t-->0){
              int n=in.nextInt();
              int[] ar=in.nextArray(n);
              PriorityQueue<int[]> pq=new PriorityQueue<>((o1, o2) -> o2[1]-o1[1]);
              ArrayList<String> ll=new ArrayList<>();
              for (int i = 0; i < n; i++) {
                  if(ar[i]>0){
                      pq.add(new int[]{i+1,ar[i]});
                  }
              }
              while (pq.size()>1){
                  int[] a1=pq.poll();
                  int[] a2=pq.poll();
                  a1[1]--;a2[1]--;
                  ll.add(a2[0]+" "+a1[0]);
                  if(a1[1]>0){
                      pq.add(a1);
                  }
                  if(a2[1]>0){
                      pq.add(a2);
                  }
              }
              out.println(ll.size());
              for(String str:ll){
                  out.println(str);
              }
          }
          out.close();
      }
      static void BFS(ArrayList<Integer>[] adj, int src, int[] dist, int[] paths, int n) {
          boolean[] visited = new boolean[n];
          for (int i = 0; i < n; i++){
              visited[i] = false;
          }
          dist[src] = 0;
          paths[src] = 1;
          Queue<Integer> q = new LinkedList<>();
          q.add(src);
          visited[src] = true;
          while (!q.isEmpty()) {
              int curr = q.peek();
              q.poll();
              for (int x : adj[curr]) {
                  if (!visited[x]) {
                      q.add(x);
                      visited[x] = true;
                  }
                  if (dist[x] > dist[curr] + 1) {
                      dist[x] = dist[curr] + 1;
                      paths[x] = paths[curr];
                  } else if (dist[x] == dist[curr] + 1){
                      paths[x] += paths[curr];
                  }
                  if(paths[x]>=1000000007){
                      paths[x]-=1000000007;
                  }
              }
          }
      }
      static void findShortestPaths(ArrayList<Integer>[] adj, int s, int n) {
          int[] dist = new int[n], paths = new int[n];
          for (int i = 0; i < n; i++){
              dist[i] = Integer.MAX_VALUE;
          }
          for (int i = 0; i < n; i++){
              paths[i] = 0;
          }
          BFS(adj, s, dist, paths, n);
          System.out.println((paths[n-1])%1000000007);
      }
      //Arrays.sort(a, (o1, o2) -> (o1[0] - o2[0]));
      static int totalPrimeFactors(int n) {
          int cnt=0;
          while (n%2==0) {
              cnt++;
              n /= 2;
          }
          int num= (int) Math.sqrt(n);
          for (int i = 3; i <= num; i+= 2) {
              while (n%i == 0) {
                  cnt++;
                  n /= i;
                  num=(int)Math.sqrt(n);
              }
          }
          if (n > 2){
              cnt++;
          }
          return cnt;
      }
      static char get(int i){
          return (char)(i+'a');
      }
      static boolean distinct(int num){
          HashSet<Integer> set=new HashSet<>();
          int len=String.valueOf(num).length();
          while (num!=0){
              set.add(num%10);
              num/=10;
          }
          return set.size()==len;
      }
      static int maxSubArraySum(int a[]) {
          int n=a.length,max=a[0],sum=a[0];
          for (int i = 1; i < n; i++) {
              sum=Math.max(sum+a[i],a[i]);
              max=Math.max(max,sum);
          }
          return max;
      }
      static void segmentedSieve(ArrayList<Integer> res,int low, int high) {
          if(low < 2){
              low = 2;
          }
          ArrayList<Integer> prime = new ArrayList<>();
          sS2(high, prime);
          boolean[] mark = new boolean[high - low + 1];
          Arrays.fill(mark, true);
          for (int i = 0; i < prime.size(); i++) {
              int loLim = (low / prime.get(i)) * prime.get(i);
              if (loLim < low){
                  loLim += prime.get(i);
              }
              if (loLim == prime.get(i)){
                  loLim += prime.get(i);
              }
              for (int j = loLim; j <= high; j += prime.get(i)) {
                  mark[j - low] = false;
              }
          }
          for (int i = low; i <= high; i++) {
              if (mark[i - low]){
                  System.out.println(i);
                  res.add(i);
              }
          }
      }
      static void sS2(int limit, ArrayList<Integer> prime) {
          int bound = (int)Math.sqrt(limit);
          boolean[] mark = new boolean[bound + 1];
          for (int i = 0; i <= bound; i++){
              mark[i] = true;
          }
          for (int i = 2; i * i <= bound; i++) {
              if (mark[i]) {
                  for (int j = i * i; j <= bound; j += i){
                      mark[j] = false;
                  }
              }
          }
          for (int i = 2; i <= bound; i++) {
              if (mark[i]){
                  prime.add(i);
              }
          }
      }
      static boolean[] sieveOfEratosthenes(int n){
          boolean[] prime = new boolean[n + 1];
          Arrays.fill(prime,true);
          prime[0]=false;prime[1]=false;
          for (int p = 2; p * p <= n; p++) {
              if(prime[p]){
                  for (int i = p * p; i <= n; i += p){
                      prime[i] = false;
                  }
              }
          }
          return prime;
      }
      static int highestPowerOf2(int n) {
          if (n < 1){ return 0; }
          int res = 1;
          for (int i = 0; i < 8 * Integer.BYTES; i++) {
              int curr = 1 << i;
              if (curr > n){ break; }
              res = curr;
          }
          return res;
      }
      static int reduceFraction(int x, int y) {
          int d= gcd(x, y);
          return x/d+y/d;
      }
      static boolean subset(int[] ar,int n,int sum){
          if(sum==0){
              return true;
          }
          if(n<0||sum<0){
              return false;
          }
          return subset(ar,n-1,sum)||subset(ar,n-1,sum-ar[n]);
      }
      static boolean isPrime(int n){
          if(n<=1) return false;
          for(int i = 2;i<=Math.sqrt(n);i++){
              if (n % i == 0) return false;
          }
          return true;
      }
      static int gcd(int a, int b) {
          if (b == 0) return a;
          return gcd(b, a % b);
      }
      static long gcd(long a, long b) {
          if (b == 0) return a;
          return gcd(b, a % b);
      }
      static long lcm(long a, long b) {
          return (a * b) / gcd(a, b);
      }
      static int lcm(int a, int b) {
          return (a * b) / gcd(a, b);
      }
      static int isPowerOfTwo(long n) {
          int ans=0;
          if(n==0){
              return ans;
          }
          while (n%2==0){
              ans++;
              n/=2;
          }
          return ans;
      }
      static boolean isPerfectSquare(int x){
          if (x >= 0) {
              int sr = (int)Math.sqrt(x);
              return ((sr * sr) == x);
          }
          return false;
      }
      static int lower_bound(int[] arr, int x) {
          int low_limit = 0, high_limit = arr.length, mid;
          while (low_limit < high_limit) {
              mid = (low_limit + high_limit) >>>1;
              if (arr[mid] >= x){
                  high_limit = mid;
              }else{
                  low_limit = mid + 1;
              }
          }
          return low_limit;
      }
      static int upper_bound(int[] arr, int x) {
          int low_limit = 0, high_limit = arr.length, mid;
          while (low_limit < high_limit) {
              mid = (low_limit + high_limit) >>> 1;
              if (arr[mid] > x){
                  high_limit = mid;
              }else{
                  low_limit = mid + 1;
              }
          }
          return low_limit;
      }
      static int binarySearch(int[] ar,int n,int num){
          int low=0,high=n-1;
          while (low<=high){
              int mid=(low+high) >>> 1;
              if(ar[mid]==num){
                  return mid;
              }else if(ar[mid]>num){
                  high=mid-1;
              }else {
                  low=mid+1;
              }
          }
          return -1;
      }
      static int fib(int n) {
          long[][] F = new long[][]{{1,1},{1,0}};
          if (n == 0){
              return 0;
          }
          power(F, n-1);
          return (int)F[0][0];
      }
      static void multiply(long F[][], long M[][]) {
          long x =  (F[0][0]*M[0][0])%1000000007 + (F[0][1]*M[1][0])%1000000007;
          long y =  (F[0][0]*M[0][1])%1000000007 + (F[0][1]*M[1][1])%1000000007;
          long z =  (F[1][0]*M[0][0])%1000000007 + (F[1][1]*M[1][0])%1000000007;
          long w =  (F[1][0]*M[0][1])%1000000007 + (F[1][1]*M[1][1])%1000000007;
          F[0][0] = x%1000000007;
          F[0][1] = y%1000000007;
          F[1][0] = z%1000000007;
          F[1][1] = w%1000000007;
      }
      static void power(long F[][], int n) {
          if( n == 0 || n == 1){
              return;
          }
          long M[][] = new long[][]{{1,1},{1,0}};
          power(F, n/2);
          multiply(F, F);
          if (n%2 != 0){
              multiply(F, M);
          }
      }
      static int binaryExponentiation(int x,int n){
          int ans=1;
          while (n>0){
              if(n%2!=0){
                  ans=(ans*x)%MOD;
              }
              x=(x*x)%MOD;
              n/=2;
          }
          return ans;
      }
      static void bfs(ArrayList<Integer>[] ar,int node){
          boolean[] visited=new boolean[ar.length];
          Queue<Integer> queue=new LinkedList<>();
          visited[node]=true;
          queue.add(node);
          while(!queue.isEmpty()){
              int nn=queue.poll();
              System.out.print(nn+" ");
              for(int n : ar[nn]) {
                  if (!visited[n]) {
                      visited[n] = true;
                      queue.add(n);
                  }
              }
          }
          System.out.println();
      }
      static void dfs(ArrayList<Integer>[] ar,int node){
          boolean[] visited=new boolean[ar.length];
          dfsUtil(ar,node,visited);
          System.out.println();
      }
      static void dfsUtil(ArrayList<Integer>[] ar,int node,boolean[] visited){
          visited[node]=true;
          //System.out.print(node+" ");
          for(Integer n:ar[node]){
              if(!visited[n]){
                  dfsUtil(ar,n,visited);
              }
          }
      }
  }