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 sys, math
  
  inf = sys.maxsize
  
  
  def get_ints(): return map(int, input().split())
  
  
  def get_array(): return list(map(int, input().split()))
  
  
  mod = 1000000007
  MOD = 998244353
  
  
  # ---------------------------------------------------------------------------------------------------------------------
  
  def main():
      for _ in range(int(input())):
          n, k = get_ints()
          arr = get_array()
          k += 1
          ans = 0
          for i in range(n):
              if i == n - 1:
                  ans += k * pow(10, arr[-1])
              else:
                  if k > 0:
                      x = pow(10, arr[i + 1] - arr[i]) - 1
                      # print(f'this is pow {x}')
                      ans += pow(10, arr[i]) * min(x, k)
                      # print(f'this is ans -> {ans}')
                      k -= min(x, k)
          print(ans.__int__())
  
  
  # ---------------------------------------------------------------------------------------------------------------------
  # Region of fastio, don't change
  
  py2 = round(0.5)
  if py2:
      from future_builtins import ascii, filter, hex, map, oct, zip
  
      range = xrange
  
  import os, sys
  from io import IOBase, BytesIO
  
  BUFSIZE = 8192
  
  
  class FastIO(BytesIO):
      newlines = 0
  
      def __init__(self, file):
          self._file = file
          self._fd = file.fileno()
          self.writable = "x" in file.mode or "w" in file.mode
          self.write = super(FastIO, self).write if self.writable else None
  
      def _fill(self):
          s = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
          self.seek((self.tell(), self.seek(0, 2), super(FastIO, self).write(s))[0])
          return s
  
      def read(self):
          while self._fill(): pass
          return super(FastIO, self).read()
  
      def readline(self):
          while self.newlines == 0:
              s = self._fill();
              self.newlines = s.count(b"\n") + (not s)
          self.newlines -= 1
          return super(FastIO, self).readline()
  
      def flush(self):
          if self.writable:
              os.write(self._fd, self.getvalue())
              self.truncate(0), self.seek(0)
  
  
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          if py2:
              self.write = self.buffer.write
              self.read = self.buffer.read
              self.readline = self.buffer.readline
          else:
              self.write = lambda s: self.buffer.write(s.encode('ascii'))
              self.read = lambda: self.buffer.read().decode('ascii')
              self.readline = lambda: self.buffer.readline().decode('ascii')
  
  
  sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip('\r\n')
  
  if __name__ == '__main__':
      main()
  