Your task is to convert a number into a string that contains raindrop sounds corresponding to certain potential factors. A factor is a number that evenly divides into another number, leaving no remainder. The simplest way to test if a number is a factor of another is to use the modulo operation.
The rules of raindrops are that if a given number:
- has 3 as a factor, add 'Pling' to the result.
- has 5 as a factor, add 'Plang' to the result.
- has 7 as a factor, add 'Plong' to the result.
- does not have any of 3, 5, or 7 as a factor, the result should be the digits of the number.