Mutual follows

You are given the follow records follows. [a, b] means that a follows b. When two people follow each other, it is called a mutual follow.

Complete the function solution, which returns the number of mutual-follow pairs. The same record does not appear twice, and there is no record of a person following themselves.

Function

solution(follows)

Constraints

• The length of follows is from 1 to 100,000.
• Each person is identified by an integer from 0 to 1,000,000, and a and b in one record are different.

Examples

Starter code

def solution(follows):
    answer = 0
    return answer