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AND Down to Zero

Medium
You are given an integer top. Find the largest integer x ≤ top such that the bitwise AND of every number from x to top inclusive equals zero.
Example 1
top=12 → 7

The AND of 8 through 12 is 8, but adding 7 (0111 in binary) brings it down to 0.

Example 2
top=1 → 0

The range [1, 1] gives 1, while [0, 1] already gives 0.

Example 3
top=32 → 31
Constraints
  • 1 ≤ top ≤ 10¹⁵
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GreedyStringSorting
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Input
top=12
Expected
7

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