description: In Berland, n different types of banknotes are used. Banknotes of the i-th type have denomination 10^{a_i} burles (burles are the currency used in Berland); the denomination of banknotes of the first type is exactly 1.
  
  Let's denote f(s) as the minimum number of banknotes required to represent exactly s burles. For example, if the denominations of banknotes used in Berland are 1, 10 and 100, then f(59) = 14: 9 banknotes with denomination of 1 burle and 5 banknotes with denomination of 10 burles can be used to represent exactly 9 ⋅ 1 + 5 ⋅ 10 = 59 burles, and there's no way to do it with fewer banknotes.
  
  For a given integer k, find the minimum positive number of burles s that cannot be represented with k or fewer banknotes (that is, f(s) > k).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — number of test cases.
  
  The first line of each test case contains two integers n and k (1 ≤ n ≤ 10; 1 ≤ k ≤ 10^9).
  
  The next line contains n integers a_1, a_2, ..., a_n (0 = a_1 < a_2 < ... < a_n ≤ 9).
  
  Output
  
  For each test case, print one integer — the minimum positive number of burles s that cannot be represented with k or fewer banknotes.
  
  Example
  
  Input
  
  
  4
  3 13
  0 1 2
  2 777
  0 4
  3 255
  0 1 3
  10 1000000000
  0 1 2 3 4 5 6 7 8 9
  
  
  Output
  
  
  59
  778
  148999
  999999920999999999
solution:  import java.util.*;
   import java.lang.*;
   import java.io.*;
  
  public class C_Banknotes
   {
       static int M = 1_000_000_007;
       static final PrintWriter out =new PrintWriter(System.out);
       static final FastReader fs = new FastReader();
       static boolean prime[];
       public static void main (String[] args) throws java.lang.Exception
       {
             
             int t= fs.nextInt();
             for(int i=0;i<t;i++)
             {
                 int n=fs.nextInt();
                 int k=fs.nextInt();
                 int a[]=fs.arrayIn(n);
                 int fgot=0;
                 long gg=0;
                 
                 long ans=0;
                 int kk=0;
                 int l=0;
                 for(int j=0;j<=9;j++){
                     if(kk<n&&a[kk]==j){
                         l=a[kk];
                         kk++;
                     }
                     if(kk==n){
                         ans=ans+(long)(k+1)*((long)Math.pow(10,l));
                         break;
                     }
                     long wee=(long)9*(long)(Math.pow(10,(j-l)));
                     if(k>=wee){
                         ans=ans+(long)9*(long)Math.pow(10,j);
                         k=k-(int)wee;
                     }else{
                            ans=ans+(long)(k+1)*((long)Math.pow(10,l));
                            break;
                     }
                 }
                 out.println(ans);
             }
             out.flush();
    }
    public static long power(long x, long y)
    {
        long temp;
        if (y == 0)
            return 1;
        temp = power(x, y / 2);
  
        if (y % 2 == 0)
            return modMult(temp,temp);
        else {
            if (y > 0)
                return modMult(x,modMult(temp,temp));
            else
                return (modMult(temp,temp)) / x;
        }
    }
    static void sieveOfEratosthenes(int n)
      {
           prime = new boolean[n + 1];
          for (int i = 0; i <= n; i++)
              prime[i] = true;
              prime[0]=false;
              if(1<=n)
              prime[1]=false;
          for (int p = 2; p * p <= n; p++)
          {
              
              if (prime[p] == true)
              {
                 
                  for (int i = p * p; i <= n; i += p)
                      prime[i] = false;
              }
          }
      }
           static class FastReader 
           {
           BufferedReader br;
           StringTokenizer st;
    
           public FastReader()
           {
               br = new BufferedReader(
                   new InputStreamReader(System.in));
           }
    
           String next()
           {
               while (st == null || !st.hasMoreElements()) {
                   try {
                       st = new StringTokenizer(br.readLine());
                       }
                   catch (IOException e) {
                       e.printStackTrace();
                       }
           }
               return st.nextToken();
           }
    
           int nextInt() { return Integer.parseInt(next()); }
    
           long nextLong() { return Long.parseLong(next()); }
    
           double nextDouble()
           {
               return Double.parseDouble(next());
           }
    
           String nextLine()
           {
               String str = "";
               try {
                   str = br.readLine();
               }
               catch (IOException e) {
                   e.printStackTrace();
               }
               return str;
           }
   int [] arrayIn(int n) throws IOException
       {
           int  arr[] = new int[n];
           for(int i=0; i<n; i++)
           {
               arr[i] = nextInt();
           }
           return arr;
       }
       }
       
       public static class Pairs implements Comparable<Pairs>
       {
           int value,index;
           Pairs(int value, int index)
           {
               this.value = value;
               this.index = index;
           }
           public int compareTo(Pairs p)
           {
               return Integer.compare(this.value, p.value);
           }
       }
       static final Random random = new Random();
    
       static void ruffleSort(int arr[])
       {
           int n = arr.length;
           for(int i=0; i<n; i++)
           {
               int j = random.nextInt(n),temp = arr[j];
               arr[j] = arr[i];
               arr[i] = temp;
           }
           Arrays.sort(arr);
       }
       static long nCk(int n, int k) {
           return (modMult(fact(n),fastexp(modMult(fact(n-k),fact(k)),M-2)));
       }
    
       static long fact (long n) {
    
           long fact =1;
           for(int i=1; i<=n; i++) {
               fact = modMult(fact,i);
           }
           return fact%M;
       }
    
       static long modMult(long a,long b) {
           return a*b%M;
       }
    
       static long fastexp(long x, int y){
           if(y==1) return x;
    
           long ans = fastexp(x,y/2);
           if(y%2 == 0) return modMult(ans,ans);
           else return modMult(ans,modMult(ans,x));
       }
   }