smallestUnusualNumber

Let’s call an integer unusual if the sum of its digits is larger than the product of its digits.
For example, the numbers 21 and 990 are unusual, while the numbers 22and 991 aren’t.

Given an integer a (represented as a string), find the smallest unusual integer x such that x ≥ a. Since both x and a can be very large, return the value of x - a.

Example

• For a = "42", the output should be smallestUnusualNumber(a) = 8.
  
  The smallest unusual number that is greater than or equal to 42 is 50, and 50 - 42 = 8.

Input/Output

• [execution time limit] 0.5 seconds

• [input] string a

  A string representing a positive integer without leading zeros.

  Guaranteed constraints:
  1 ≤ a.length ≤ 102.

• [output] integer

  • The difference between the smallest unusual number that is larger than or equal to a, and a.