hackerrank - Sock Merchant - python3

hackerrank - Sock Merchant - python3

#!/bin/python3
import sys

n = 10
arr = [1, 1, 3, 1, 2, 1, 3, 3, 3, 3 ]

arr_m = {}
def calculatePairs(a,arr):
    match_count = 0
    for item in arr:
        if item == a:
            match_count = match_count + 1
    if match_count%2 == 0:
        match_count =  match_count/2
    else:
        match_count = match_count - 1
        match_count = match_count/2

    return match_count

def main():
    n = input()
    arr = input().split(" ")
    #print(arr)
    #return

    for a in arr: 
        mc =  calculatePairs(a,arr)
        arr_m[a] = mc

    result = 0
    for key in arr_m:
        #print(arr_m[key])
        result = result + int(arr_m[key])

    print(result)
if __name__ == '__main__':
    main()