You are given a string s containing lowercase English letters and digits. Repeatedly perform the following operation until no digits remain in s:

Choose any digit character in s, delete that digit, and also delete the closest lowercase letter to its left.

Return the final string after all possible operations have been applied.

Note: The input is constructed so that every digit can be removed by repeatedly deleting a digit together with a letter to its left.

Constraints:

• $1 \leq$ s.length $\leq 100$

• s consists only of lowercase English letters and digits

• The input is generated such that it is possible to delete all digits

Input: s = "a1b2c3"-str
Output: ""-str
Explanation: Each digit removes itself and the closest letter to its left: a1 is removed, then b2, then c3, leaving an empty string.

Input: s = "z9"-str
Output: ""-str
Explanation: The digit 9 is removed along with the closest letter to its left (z), leaving an empty string.

Input: s = "ab12cd3e4"-str
Output: "c"-str
Explanation: Processing left to right with stack-like behavior: 1 removes b (leaving a), 2 removes a (leaving none), then c and d are added, 3 removes d (leaving c), e is added, and 4 removes e, so c remains.

Input: s = "mno0p1q2r3s4"-str
Output: "mn"-str
Explanation: Each digit deletes the nearest letter to its left: 0 removes o (leaving mn), 1 removes p, 2 removes q, 3 removes r, and 4 removes s, so the final remaining string is "mn".

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