code: def StrToInt(input_string, bitlength):
      
      try:
          return BVV(int(input_string.value), bitlength)
      except ValueError:
          return BVV(-1, bitlength)
docs: Return True if the concrete value of the input_string ends with suffix
      otherwise false.
  
      :param input_string: the string we want to transform in an integer
      :param bitlength: bitlength of the bitvector representing the index of the substring
  
      :return BVV: bit-vector representation of the integer resulting from ythe string or -1 in bitvector representation
                   if the string cannot be transformed into an integer