A post spreading through shares

There are n users on a social network, numbered from 0 to n - 1. A record [a, b] in follows means that a follows b, so a post that b shares appears in a's feed.

Person start writes a post and shares it. Everyone whose feed shows this post reshares it. Complete the function solution, which returns the number of people, not counting start, whose feed shows this post at least once.

Function

solution(n, follows, start)

Constraints

• n is an integer from 1 to 100,000.
• The length of follows is from 0 to 100,000.
• Each element of follows has the form [a, b], where a and b are different integers from 0 to n - 1. The same record never appears twice.
• start is an integer from 0 to n - 1.

Examples

Starter code

def solution(n, follows, start):
    answer = 0
    return answer