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 javax.swing.plaf.basic.BasicInternalFrameTitlePane.SystemMenuBar;
  
  import java.lang.*;
  import java.io.*;
  
  public class Main
  {
   public static class FastReader {
  
  		BufferedReader b;
  		StringTokenizer s;
  		public FastReader() {
  			b=new BufferedReader(new InputStreamReader(System.in));
  		}
  		String next() {
  			while(s==null ||!s.hasMoreElements()) {
  				try {
  					s=new StringTokenizer(b.readLine());
  				}
  				catch(IOException e) {
  					e.printStackTrace();
  				}
  			}
  			return s.nextToken();
  		}
  		public int nextInt() {
  			return Integer.parseInt(next());
  		}
  		public long nextLong() {
  			return Long.parseLong(next());
  		}
  		public double nextDouble() {
  			return Double.parseDouble(next());
  		}
  		
  		String nextLine() {
  			String str="";
  			try {
  				str=b.readLine();
  			}
  			catch(IOException e) {
  				e.printStackTrace();
  			}
  			return str;
  		}
  		boolean hasNext() {
  		    if (s != null && s.hasMoreTokens()) {
  		        return true;
  		    }
  		    String tmp;
  		    try {
  		        b.mark(1000);
  		        tmp = b.readLine();
  		        if (tmp == null) {
  		            return false;
  		        }
  		        b.reset();
  		    } catch (IOException e) {
  		        return false;
  		    }
  		    return true;
  		}
  	
  }
   
   public static long gcd(long a,long b) {if(a==0)return b; return gcd(b%a,a);}
   public static int gcd(int a,int b) {if(a==0)return b; return gcd(b%a,a);};
   
   static int power(int x, int y){
       if (y == 0)
           return 1;
       else if (y % 2 == 0)
           return power(x, y / 2) * power(x, y / 2);
       else
           return x * power(x, y / 2) * power(x, y / 2);
   }
   
   static long power(long x , long y)
   {
  	 if (y == 0)
           return 1;
       else if (y % 2 == 0)
           return power(x, y / 2) * power(x, y / 2);
       else
           return x * power(x, y / 2) * power(x, y / 2);
   }
   
   
  	
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		
  		long mod=1000000007;
  		
  		FastReader in=new FastReader();
  		if(in.hasNext()){
  		  
  		if(in.hasNext()){
  		
  		BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
  		
  		int test=in.nextInt();
  		while(test-->0)
  		{
  			int n=in.nextInt();
  			long k=in.nextLong();
  			k++;
  			long arr[]=new long[n];
  			
  			for(int i=0;i<n;i++)
  			{
  				long t=in.nextLong();
  				arr[i]=t;
  			}
  			long fk=0,tk=0;
  			long term=0;
  			int i=0;
  			while(i<n-1)
  			{
  				tk=power((long)10,arr[i+1]-arr[i])-(long)1;
  				fk+=tk;
  				if(fk>=k) {fk-=tk;
  					break;}
  				term+=tk*power((long)10,arr[i]);
  				i++;
  			}
  			
  				term+=power((long)10,arr[i])*(k-fk);
  			
  				//term+=power((long)10,arr[i])*(k-fk);
  			
  				
  				System.out.println(term);
  				
  			log.flush();
  		}
  		
  	}
  	}
  }
  }