class Solution(object):
    def maxDifference(self, s):
        dicti = {}
        for c in s:
            if c not in dicti:
                dicti[c] = 0
            dicti[c] +=1
        evenChars = []
        oddChars = []
        for key in dicti:
            if dicti[key] % 2 == 0:
                evenChars.append(key)
            else:
                oddChars.append(key)
 
        evenChars = sorted(evenChars, key=lambda x:dicti[x])
        oddChars = sorted(oddChars, key=lambda x:dicti[x])
        return dicti[oddChars[-1]] - dicti[evenChars[0]]

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