cwMinId

def next_id(arr):
    from itertools import groupby
    #your code here.
    # 1 sort array 0-> max
    # 2 kill duplicates
    # 3 compare counter with array items - return current counter if unequal
    # return counter++

    def sortCopyArr(arr):
        b = arr[:]
        b.sort()
        return b

    def removeDuplEl(arr):
        new_arr = [el for el, _ in groupby(arr)]
        return new_arr

    if (len(arr) == 0):
        return 0

    arr = removeDuplEl(sortCopyArr(arr))
    i = 0
    for i in range(len(arr)):
        if(i != arr[i]):
            return i
    #print (i)
    return (i + 1)