Given two integer arrays where the second array is a shuffled duplicate of the first array with one element missing, find the missing element.
Please note, there may be duplicates in the arrays, so checking if a numerical value exists in one and not the other is not a valid solution.
```
find_missing([1, 2, 2, 3], [1, 2, 3]) => 2
```
```
find_missing([6, 1, 3, 6, 8, 2], [3, 6, 6, 1, 2]) => 8
```
The first array will always have at least one element.
def find_missing(arr1, arr2):
    for x in set(arr1):
        if arr1.count(x) != arr2.count(x): return x

def find_missing(arr1, arr2):
    for x in set(arr1):
        if arr1.count(x) != arr2.count(x): return x
