class Solution:
    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
        if len(s) == len(set(s)):
            return -1

        indices: dict = {}

        for index, char in enumerate(s):
            if char in indices:
                indices[char].append(index)
            else:
                indices[char] = [index]

        peak: int = 0
        for key, value in indices.items():
            span: int = max(value) - min(value) - 1
            peak = max(peak, span)

        return peak