In an array of integers, find out odd occurring integer in O(n) time. Given all numbers appear even times except one integer code example

Example: you are given an array of integers. your task is to print the sum of numbers that occurs for an even number of times in the array.

import collections
def fun(arr):
    mp = collections.defaultdict(int)
      
    for i in range(len(arr)):
        mp[arr[i]] += 1 
    sum = 0 
    for i in mp.keys(): 
          
        
        if (mp[i] % 2 == 0): 
            sum += i
    return sum
n= int(input())
arr = list(map(int,input().split()))
print(fun(arr))