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.*;
  import java.util.*;
  
  public class Main {
  	static InputReader in = new InputReader(System.in);
  	static OutputWriter out = new OutputWriter(System.out);
  
  	public static void main(String[] args) throws IOException {
  		int t = i();
  		int c = 1;
  		while (t-- > 0) {
  			solve();
  			c++;
  		}
  		out.close();
  
  	}
  
  	static int mod = 1000000007;
  	static StringBuilder sb;
  
  	private static void solve() {
          int n =i();
          PriorityQueue<Pair> pq = new PriorityQueue<Pair>((a,b)->b.sp-a.sp);
  
          for(int i=0;i<n;i++){
              int val =i();
              if(val!=0){
                  pq.add(new Pair(val,i+1));
              }
          }
          ArrayList<Pair> arr = new ArrayList<Pair>();
          int count=0;
          int flag=1;
          while(pq.size()>1){
              flag=0;
              Pair first=pq.poll();
              Pair second=pq.poll();
              count++;
              arr.add(new Pair(first.ep,second.ep));
              int val1 =first.sp-1;
              int val2=second.sp-1;
              if(val1!=0){
                  pq.add(new Pair(val1,first.ep));
              }
              if(val2!=0){
                  pq.add(new Pair(val2,second.ep));
              }
          }
          if(flag==1){
              System.out.println(0);
  
          }else{
              System.out.println(count);
              for(int i=0; i<arr.size(); i++){
                  System.out.println(arr.get(i).sp+" "+arr.get(i).ep);
              }
          }
         
  	}
  
  	private static void mark(int i, int e, int s, char[][] arr, boolean[][] vis) {
  		while (s <= e) {
  			vis[i][s] = true;
  			vis[i][e] = true;
  			i++;
  			s++;
  			e--;
  		}
  	}
  
  	private static boolean check(int i, int s, int e, char[][] arr, boolean[][] vis) {
  		if (i == arr.length) {
  			return false;
  		}
  		if (arr[i][s] == arr[i][e] && arr[i][s] == '*') {
  			if (s == e) {
  				return true;
  			} else {
  				return check(i + 1, s + 1, e - 1, arr, vis);
  			}
  		}
  		return false;
  	}
  
  	// Fenwick Tree
  	static class fenwickTree {
  		int n;
  		long[] farr;
  
  		fenwickTree(int n, long[] a) {
  			this.n = n;
  			farr = new long[n + 1];
  			for (int i = 0; i < n; i++) {
  				update(i + 1, a[i]);
  			}
  		}
  
  		void update(int i, long val) {
  			while (i < farr.length) {
  				farr[i] += val;
  				i += (i & -i);
  			}
  		}
  
  		long sum(int i) {
  			long sum = 0L;
  			while (i > 0) {
  				sum += farr[i];
  				i -= (i & -i);
  			}
  			return sum;
  		}
  	}
  
  // ****CLASS PAIR ************************************************
  	static class Pair implements Comparable<Pair> {
  		int sp;
  		int ep;
  
  		Pair(int sp, int ep) {
  			this.sp = sp;
  			this.ep = ep;
  		}
  
  		public int compareTo(Pair o) {
  			return this.sp - o.sp;
  		}
  
  	}
  
  	// static class Pair implements Comparable<Pair> {
  	// 	char ch;
  	// 	ArrayList<Integer> idxs;
  
  	// 	Pair(char ch, ArrayList<Integer> idxs) {
  	// 		this.ch = ch;
  	// 		this.idxs = idxs;
  	// 	}
  
  	// 	public int compareTo(Pair o) {
  	// 		return o.idxs.size() - this.idxs.size();
  	// 	}
  
  	// }
  
  	static class Edge implements Comparable<Edge> {
  		int u;
  		int v;
  		int wt;
  
  		Edge(int u, int v, int wt) {
  			this.u = u;
  			this.v = v;
  			this.wt = wt;
  		}
  
  		public int compareTo(Edge o) {
  			return this.wt - o.wt;
  		}
  	}
  
  // *************Disjoint set
  // union*********//
  	static class dsu {
  		int[] par;
  		int[] rank;
  
  		dsu(int n) {
  			par = new int[n + 1];
  			rank = new int[n + 1];
  			for (int i = 0; i <= n; i++) {
  				par[i] = i;
  				rank[i] = 1;
  			}
  		}
  
  		int find(int a) {
  			if (par[a] == a) {
  				return a;
  			}
  			int x = find(par[a]);
  			par[a] = x;
  			return x;
  		}
  
  		boolean union(int a, int b) {
  			int pa = find(a);
  			int pb = find(b);
  			if (pa == pb) {
  				return false;
  			}
  			if (rank[pa] > rank[pb]) {
  				par[pb] = pa;
  			} else if (rank[pb] > rank[pa]) {
  				par[pa] = pb;
  			} else {
  				par[pa] = pb;
  				rank[pb]++;
  			}
  			return true;
  		}
  
  	}
  
  	// **************NCR%P******************
  	static long ncr(int n, int r) {
  		if (r > n)
  			return (long) 0;
  		long[] fact = new long[(int) 1e6 + 10];
  		fact[0] = fact[1] = 1;
  		for (int i = 2; i < fact.length; i++) {
  			fact[i] = ((long) (i % mod) * (long) (fact[i - 1] % mod)) % mod;
  		}
  		long res = fact[n] % mod;
  		res = ((long) (res % mod) * (long) (p(fact[r], mod - 2) % mod)) % mod;
  		res = ((long) (res % mod) * (long) (p(fact[n - r], mod - 2) % mod)) % mod;
  		return res;
  	}
  
  	static ArrayList<Integer> divisors(int n) {
  		ArrayList<Integer> al = new ArrayList<>();
  		for (int i = 1; i * i <= n; i++) {
  			if (n % i == 0) {
  				if (n == i * i) {
  					al.add(i);
  				} else {
  					al.add(i);
  					al.add(n / i);
  				}
  			}
  		}
  		Collections.sort(al);
  		return al;
  	}
  
  	static long p(long x, long y)// POWER FXN //
  	{
  		if (y == 0)
  			return 1;
  
  		long res = 1;
  		while (y > 0) {
  			if (y % 2 == 1) {
  				res = (res * x) % mod;
  				y--;
  			}
  
  			x = (x * x) % mod;
  			y = y / 2;
  
  		}
  		return res;
  	}
  
  	private static boolean pow2(int i) {
  		return (i & (i - 1)) == 0;
  	}
  
  	private static void sort(int[] arr) {
  		int n = arr.length;
  		ArrayList<Integer> res = new ArrayList<>();
  		for (int a : arr) {
  			res.add(a);
  		}
  		Collections.sort(res);
  		for (int i = 0; i < n; i++) {
  			arr[i] = res.get(i);
  		}
  	}
  
  	private static void sort(long[] arr) {
  		int n = arr.length;
  		ArrayList<Long> res = new ArrayList<>();
  		for (long a : arr) {
  			res.add(a);
  		}
  		Collections.sort(res);
  		for (int i = 0; i < n; i++) {
  			arr[i] = res.get(i);
  		}
  	}
  
  	private static void revSort(int[] arr) {
  		int n = arr.length;
  		ArrayList<Integer> res = new ArrayList<>();
  		for (int a : arr) {
  			res.add(a);
  		}
  		Collections.sort(res, Collections.reverseOrder());
  		for (int i = 0; i < n; i++) {
  			arr[i] = res.get(i);
  		}
  	}
  
  	private static ArrayList<Integer> sieveOfEratosthenes(int n) {
  		boolean[] arr = new boolean[n + 1];
  
  		arr[0] = arr[1] = true;
  		for (int i = 2; i * i <= n; i++) {
  			if (!arr[i]) {
  				for (int j = i * i; j <= n; j += i) {
  					arr[j] = true;
  				}
  			}
  		}
  		ArrayList<Integer> primes = new ArrayList<>();
  		for (int i = 2; i <= n; i++) {
  			if (!arr[i]) {
  				primes.add(i);
  			}
  		}
  		return primes;
  	}
  
  	private static ArrayList<Integer> segmentedSieve(int s, int e) {
  		int len = (int) (Math.sqrt(e) + 1);
  		ArrayList<Integer> primes = sieveOfEratosthenes(len);
  		boolean[] arr2 = new boolean[e - s + 1];
  		if (s == 1) {
  			arr2[0] = true;
  		}
  		ArrayList<Integer> res = new ArrayList<>();
  		for (int p : primes) {
  
  			int st = (int) (p * (Math.ceil((double) s / p)));
  			if (st < s) {
  				st += p;
  			}
  			if (st == p) {
  				st += p;
  			}
  			for (int i = st; i <= e; i += p) {
  				arr2[i - s] = true;
  			}
  		}
  		for (int i = 0; i < arr2.length; i++) {
  			if (!arr2[i]) {
  				res.add(i + s);
  			}
  		}
  		return res;
  	}
  
  	private static long pow(int n, int k) {
  		long res = 1;
  		long num = (long) n;
  		while (k > 0) {
  			if ((k & 1) == 1) {
  				res = (res * num) % mod;
  			}
  			k /= 2;
  			num = num * num % mod;
  		}
  		return res;
  	}
  
  	private static int countDigits(int n) {
  		int c = 0;
  		while (n != 0) {
  			c++;
  			n /= 10;
  		}
  		return c;
  	}
  
  	private static boolean palindrome(String str) {
  		int s = 0;
  		int e = str.length() - 1;
  		while (s < e) {
  			if (str.charAt(s) != str.charAt(e)) {
  				return false;
  			}
  			s++;
  			e--;
  		}
  		return true;
  	}
  
  	private static void reverse(int[] arr, int s, int e) {
  		while (s < e) {
  			int temp = arr[s];
  			arr[s++] = arr[e];
  			arr[e--] = temp;
  		}
  	}
  
  	private static int getMax(int[] arr, int s, int e) {
  		int maxi = s;
  		for (int i = s + 1; i <= e; i++) {
  			if (arr[i] > arr[maxi]) {
  				maxi = i;
  			}
  		}
  		return maxi;
  	}
  
  	private static int getMin(int[] arr, int s, int e) {
  		int mini = s;
  		for (int i = s + 1; i <= e; i++) {
  			if (arr[i] < arr[mini]) {
  				mini = i;
  			}
  		}
  		return mini;
  	}
  
  	// ******LOWEST COMMON MULTIPLE************************
  	private static long lcm(long n1, long n2) {
  		return (n1 * n2) / gcd(n1, n2);
  	}
  
  	private static int lcm(int n1, int n2) {
  		return (n1 * n2) / gcd(n1, n2);
  	}
  
  	// ***********GCD*****************
  	private static long gcd(long num1, long num2) {
  		if (num2 == 0) {
  			return num1;
  		}
  		return gcd(num2, num1 % num2);
  	}
  
  	private static int gcd(int num1, int num2) {
  		if (num2 == 0) {
  			return num1;
  		}
  		return gcd(num2, num1 % num2);
  	}
  
  	// **************PRIME FACTORIZE **********************************//
  	static TreeMap<Long, Long> prime(long n) {
  		TreeMap<Long, Long> h = new TreeMap<>();
  		long num = n;
  		for (int i = 2; i <= Math.sqrt(num); i++) {
  			if (n % i == 0) {
  				long nt = 0L;
  				while (n % i == 0) {
  					n = n / i;
  					nt++;
  				}
  				h.put(i * 1L, nt);
  			}
  		}
  		if (n != 1)
  			h.put(n, 1L);
  		return h;
  
  	}
  
  	static class InputReader {
  		private InputStream stream;
  		private byte[] buf = new byte[1024];
  		private int curChar;
  		private int numChars;
  		private SpaceCharFilter filter;
  
  		public InputReader(InputStream stream) {
  			this.stream = stream;
  		}
  
  		public int read() {
  			if (numChars == -1)
  				throw new InputMismatchException();
  			if (curChar >= numChars) {
  				curChar = 0;
  				try {
  					numChars = stream.read(buf);
  				} catch (IOException e) {
  					throw new InputMismatchException();
  				}
  				if (numChars <= 0)
  					return -1;
  			}
  			return buf[curChar++];
  		}
  
  		public int Int() {
  			int c = read();
  			while (isSpaceChar(c))
  				c = read();
  			int sgn = 1;
  			if (c == '-') {
  				sgn = -1;
  				c = read();
  			}
  			int res = 0;
  			do {
  				if (c < '0' || c > '9')
  					throw new InputMismatchException();
  				res *= 10;
  				res += c - '0';
  				c = read();
  			} while (!isSpaceChar(c));
  			return res * sgn;
  		}
  
  		public String String() {
  			int c = read();
  			while (isSpaceChar(c))
  				c = read();
  			StringBuilder res = new StringBuilder();
  			do {
  				res.appendCodePoint(c);
  				c = read();
  			} while (!isSpaceChar(c));
  			return res.toString();
  		}
  
  		public boolean isSpaceChar(int c) {
  			if (filter != null)
  				return filter.isSpaceChar(c);
  			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
  		}
  
  		public String next() {
  			return String();
  		}
  
  		public interface SpaceCharFilter {
  			public boolean isSpaceChar(int ch);
  		}
  	}
  
  	static class OutputWriter {
  		private final PrintWriter writer;
  
  		public OutputWriter(OutputStream outputStream) {
  			writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
  		}
  
  		public OutputWriter(Writer writer) {
  			this.writer = new PrintWriter(writer);
  		}
  
  		public void print(Object... objects) {
  			for (int i = 0; i < objects.length; i++) {
  				if (i != 0)
  					writer.print(' ');
  				writer.print(objects[i]);
  			}
  		}
  
  		public void println(Object... objects) {
  			print(objects);
  			writer.println();
  		}
  
  		public void close() {
  			writer.close();
  		}
  
  		public void flush() {
  			writer.flush();
  		}
  	}
  
  	public static int i() {
  		return in.Int();
  	}
  
  	public static long l() {
  		String s = in.String();
  		return Long.parseLong(s);
  	}
  
  	public static String s() {
  		return in.String();
  	}
  
  	public static int[] readArray(int n) {
  		int A[] = new int[n];
  		for (int i = 0; i < n; i++) {
  			A[i] = i();
  		}
  		return A;
  	}
  
  	public static long[] readArray(long n) {
  		long A[] = new long[(int) n];
  		for (int i = 0; i < n; i++) {
  			A[i] = l();
  		}
  		return A;
  	}
  
  }
  