description: Shohag has an integer sequence a_1, a_2, …, a_n. He can perform the following operation any number of times (possibly, zero):
  
    * Select any positive integer k (it can be different in different operations). 
    * Choose any position in the sequence (possibly the beginning or end of the sequence, or in between any two elements) and insert k into the sequence at this position. 
    * This way, the sequence a changes, and the next operation is performed on this changed sequence. 
  
  
  
  For example, if a=[3,3,4] and he selects k = 2, then after the operation he can obtain one of the sequences [\underline{2},3,3,4], [3,\underline{2},3,4], [3,3,\underline{2},4], or [3,3,4,\underline{2}].
  
  Shohag wants this sequence to satisfy the following condition: for each 1 ≤ i ≤ |a|, a_i ≤ i. Here, |a| denotes the size of a.
  
  Help him to find the minimum number of operations that he has to perform to achieve this goal. We can show that under the constraints of the problem it's always possible to achieve this goal in a finite number of operations.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 200) — the number of test cases.
  
  The first line of each test case contains a single integer n (1 ≤ n ≤ 100) — the initial length of the sequence.
  
  The second line of each test case contains n integers a_1, a_2, …, a_n (1 ≤ a_i ≤ 10^9) — the elements of the sequence.
  
  Output
  
  For each test case, print a single integer — the minimum number of operations needed to perform to achieve the goal mentioned in the statement.
  
  Example
  
  Input
  
  
  4
  3
  1 3 4
  5
  1 2 5 7 4
  1
  1
  3
  69 6969 696969
  
  
  Output
  
  
  1
  3
  0
  696966
  
  Note
  
  In the first test case, we have to perform at least one operation, as a_2=3>2. We can perform the operation [1, 3, 4] → [1, \underline{2}, 3, 4] (the newly inserted element is underlined), now the condition is satisfied.
  
  In the second test case, Shohag can perform the following operations:
  
  [1, 2, 5, 7, 4] → [1, 2, \underline{3}, 5, 7, 4] → [1, 2, 3, \underline{4}, 5, 7, 4] → [1, 2, 3, 4, 5, \underline{3}, 7, 4].
  
  In the third test case, the sequence already satisfies the condition.
solution: 					/*
  					ID: abdelra29
  LANG: JAVA
  PROG: zerosum
  					*/
  						/*
  						TO LEARN
  				
  						2-euler tour
  					
  						*/
  						/*
  						TO SOLVE 
  						codeforces 722 kavi on pairing duty
  						*/
  						/*
  						bit manipulation shit
  						1-Computer Systems: A Programmer's Perspective
  						2-hacker's delight
  						*/
  						/*
  						TO WATCH
  						
  						*/
  						            import java.util.*;
  								    import java.math.*;
  								    import java.io.*; 
  								    import java.util.stream.Collectors;
  
  								       public class A{
  						            static FastScanner scan=new FastScanner();
  									     public static PrintWriter out = new PrintWriter (new BufferedOutputStream(System.out));
  									     static boolean vis[][];
  	
  
  
  				public static void main(String[] args)  throws Exception 
  						      {
  						
  
  						 /*
  						 very important tips 
  						 1-just fucking think backwards once in your shitty life
  						 2-consider brute forcing and finding some patterns and observations
  						 3-when you're in contest don't get out because you think there is no enough time
  						
  						 */
  						
  							//scan=new FastScanner("binary.in");
  								///out = new PrintWriter("zerosum.out");
  								 
  								 							 /*
  								 READING 
  							
  								 3-Introduction to DP with Bitmasking codefoces
  								 4-Bit Manipulation hackerearth
  								 5-read more about mobious and inculsion-exclusion 
  								 */
  								 /*
  								
  								 */
  								
  					
  								    int tt=1;
  				
  						
  
  
  	tt=scan.nextInt();
  
  								int T=1;
  								 outer:while(tt-->0)
  								    {
  int n=scan.nextInt();
  int arr[]=new int[n];
  int max=0,id=-1;
  for(int i=0;i<n;i++){
  	arr[i]=scan.nextInt();
  	if(arr[i]-(i+1)>max)
  	{
  		max=(arr[i]-(i+1));
  	}
  }
  out.println(max);
  
  	 }
  
  								
  
  		out.close();
  					}
  					
  			
  
  
  					static class special{
  					boolean is;
  					char c;
  					public special(boolean is,char c)
  					{
  						this.is=is;
  						this.c=c;
  					}
  
  						 @Override
  								            public int hashCode() {
  								                return (int)(c+ 31 *(is?1:0));
  								            }
  						  @Override
  								            public boolean equals(Object o){
  								            //	System.out.println("FUCK");
  								                if (o == this) return true;
  								                if (o.getClass() != getClass()) return false;
  								                special t = (special)o;
  								                return t.is == is && t.c == c;
  								            }
  					}
  		
  								   
  								    
  								  
  								     static class FastScanner
  						{
  						    private int BS = 1 << 16;
  						    private char NC = (char) 0;
  						    private byte[] buf = new byte[BS];
  						    private int bId = 0, size = 0;
  						    private char c = NC;
  						    private double cnt = 1;
  						    private BufferedInputStream in;
  						 
  						    public FastScanner() {
  						        in = new BufferedInputStream(System.in, BS);
  						    }
  						 
  						    public FastScanner(String s) {
  						        try {
  						            in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
  						        } catch (Exception e) {
  						            in = new BufferedInputStream(System.in, BS);
  						        }
  						    }
  						 
  						    private char getChar() {
  						        while (bId == size) {
  						            try {
  						                size = in.read(buf);
  						            } catch (Exception e) {
  						                return NC;
  						            }
  						            if (size == -1) return NC;
  						            bId = 0;
  						        }
  						        return (char) buf[bId++];
  						    }
  						 
  						    public int nextInt() {
  						        return (int) nextLong();
  						    }
  						 
  						    public int[] nextInts(int N) {
  						        int[] res = new int[N];
  						        for (int i = 0; i < N; i++) {
  						            res[i] = (int) nextLong();
  						        }
  						        return res;
  						    }
  						 
  						    public long[] nextLongs(int N) {
  						        long[] res = new long[N];
  						        for (int i = 0; i < N; i++) {
  						            res[i] = nextLong();
  						        }
  						        return res;
  						    }
  						 
  						    public long nextLong() {
  						        cnt = 1;
  						        boolean neg = false;
  						        if (c == NC) c = getChar();
  						        for (; (c < '0' || c > '9'); c = getChar()) {
  						            if (c == '-') neg = true;
  						        }
  						        long res = 0;
  						        for (; c >= '0' && c <= '9'; c = getChar()) {
  						            res = (res << 3) + (res << 1) + c - '0';
  						            cnt *= 10;
  						        }
  						        return neg ? -res : res;
  						    }
  						 
  						    public double nextDouble() {
  						        double cur = nextLong();
  						        return c != '.' ? cur : cur + nextLong() / cnt;
  						    }
  						 
  						    public double[] nextDoubles(int N) {
  						        double[] res = new double[N];
  						        for (int i = 0; i < N; i++) {
  						            res[i] = nextDouble();
  						        }
  						        return res;
  						    }
  						 
  						    public String next() {
  						        StringBuilder res = new StringBuilder();
  						        while (c <= 32) c = getChar();
  						        while (c > 32) {
  						            res.append(c);
  						            c = getChar();
  						        }
  						        return res.toString();
  						    }
  						 
  						    public String nextLine() {
  						        StringBuilder res = new StringBuilder();
  						        while (c <= 32) c = getChar();
  						        while (c != '\n') {
  						            res.append(c);
  						            c = getChar();
  						        }
  						        return res.toString();
  						    }
  						 
  						    public boolean hasNext() {
  						        if (c > 32) return true;
  						        while (true) {
  						            c = getChar();
  						            if (c == NC) return false;
  						            else if (c > 32) return true;
  						        }
  						    }
  						}
  
  								     static class Pair implements Comparable<Pair>{
  								            public long x, y,z;
  								            public Pair(long x1, long y1,long z1) {
  								                x=x1;
  								                y=y1;
  								                z=z1;
  								            }
  								             public Pair(long x1, long y1) {
  								                x=x1;
  								                y=y1;
  								    
  								            }
  								            
  								            @Override
  								            public int hashCode() {
  								                return (int)(x + 31 * y);
  								            }
  								            public String toString() {
  								                return x + " " + y+" "+z;
  								            }
  								            @Override
  								            public boolean equals(Object o){
  								                if (o == this) return true;
  								                if (o.getClass() != getClass()) return false;
  								                Pair t = (Pair)o;
  								                return t.x == x && t.y == y&&t.z==z;
  								            }
  								    public int compareTo(Pair o)
  								    {
  								  	
  								return (int)(x-o.x);
  								     
  								        }
  								     
  								    }
  								}
  
  								
  								    
  								   
  
  								     
  