In this task, you need to count the occurrences of the given word in the given sentence.

Example Input: Sentence: 'painting of a ship in grass with lighthouse in background'. Count the occurrences of the word 'in' in the given sentence.
Example Output: 2

Example Input: Sentence: 'giraffe with front legs spread looking at water'. Count the occurrences of the word 'legs' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a boy on an off road skateboard coming down a green grass hill with trees behind him'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
2