Convert a string to alternating case, where even-indexed characters are lowercase and odd-indexed characters are uppercase.
Examples:
Input: input = "hello"
Output: "hElLo"
Explanation: Characters at indices 0, 2, 4 (h, l, o) are lowercase; characters at indices 1, 3 (e, l) are uppercase
Input: input = "salesforce"
Output: "sAlEsFoRcE"
Explanation: Characters at even positions (0, 2, 4, 6, 8) are lowercase; characters at odd positions (1, 3, 5, 7) are uppercase
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