description: During the hypnosis session, Nicholas suddenly remembered a positive integer n, which doesn't contain zeros in decimal notation. 
  
  Soon, when he returned home, he got curious: what is the maximum number of digits that can be removed from the number so that the number becomes not prime, that is, either composite or equal to one?
  
  For some numbers doing so is impossible: for example, for number 53 it's impossible to delete some of its digits to obtain a not prime integer. However, for all n in the test cases of this problem, it's guaranteed that it's possible to delete some of their digits to obtain a not prime number.
  
  Note that you cannot remove all the digits from the number.
  
  A prime number is a number that has no divisors except one and itself. A composite is a number that has more than two divisors. 1 is neither a prime nor a composite number.
  
  Input
  
  Each test contains multiple test cases.
  
  The first line contains one positive integer t (1 ≤ t ≤ 10^3), denoting the number of test cases. Description of the test cases follows.
  
  The first line of each test case contains one positive integer k (1 ≤ k ≤ 50) — the number of digits in the number.
  
  The second line of each test case contains a positive integer n, which doesn't contain zeros in decimal notation (10^{k-1} ≤ n < 10^{k}). It is guaranteed that it is always possible to remove less than k digits to make the number not prime.
  
  It is guaranteed that the sum of k over all test cases does not exceed 10^4.
  
  Output
  
  For every test case, print two numbers in two lines. In the first line print the number of digits, that you have left in the number. In the second line print the digits left after all delitions. 
  
  If there are multiple solutions, print any.
  
  Example
  
  Input
  
  
  7
  3
  237
  5
  44444
  3
  221
  2
  35
  3
  773
  1
  4
  30
  626221626221626221626221626221
  
  
  Output
  
  
  2
  27
  1
  4
  1
  1
  2
  35
  2
  77
  1
  4
  1
  6
  
  Note
  
  In the first test case, you can't delete 2 digits from the number 237, as all the numbers 2, 3, and 7 are prime. However, you can delete 1 digit, obtaining a number 27 = 3^3.
  
  In the second test case, you can delete all digits except one, as 4 = 2^2 is a composite number.
solution: # l,r = list(map(int,input().split()))
  
  
  # l<=r
  
  t = int(input())
  
  prime2 = []
  
  for i in range(2,1000):
      prime = True
      for j in prime2:
          if i%j == 0:
              prime = False
              break
      
      if prime: prime2.append(i)
  
  
  def digits(i,k,s,out,n):
      if len(out)>0:
          test = int(out)
          for prime in prime2:
              if prime == test: break
              if prime>test: return out
  
      if n == 0:
          return ""
  
      for j in range(i+1,k):
          outt = digits(j,k,s,out+s[j],n-1)
          if outt != "":
              return outt
  
      return ""
  
  for i in range(t):
      k = int(input())
      s = input()
  
      for i in range(1,k+1):
          out = digits(-1,k,s,"",i)
          if out != "":
              print(len(out))
              print(out)
              break
  
  
  
      # found = False
      # for c in s:
      #     if c not in prime1:
      #         print(1)
      #         print(c)
      #         found = True
      #         break
      
      # if found: continue
  
      # if "2" in s[1:]:
      #     print("2")
      #     print(s[0]+"2")
      #     continue
      # if "5" in s[1:]:
      #     print("5")
      #     print(s[0]+"5")
      #     continue
  
  
  
      # get all possible 2 digit numbers, check if they are prime
      
      # adding up digits will eventually equal 3,6,9 if it is a mutiple of 3
      # 7
  
      # if there is 2 of the same number
      # if there is a 4, 6, 8, 0, 1
      # if there is a 2, 5 in the non first digit
      # if the sum of the digits is divisible by 3
  
  