Relay Coverage Gap

You are deploying relay stations along a line. Some points have specific signal types. You are given a target set of signal types (as a string of characters) that must all be present in your window. Additionally, to ensure connectivity, the distance (difference in indices) between any two consecutive signal-carrying points in your window must not exceed G. Find the length of the shortest window that satisfies both conditions. Input Format: - Line 1: Integer G (max gap). - Line 2: A string of unique characters representing the target signal types. - Line 3: A string representing the available signals at each index ('.' means no signal). Output Format: - A single integer representing the minimum length, or 0 if impossible. Example: Input: 2 AB A..B.A Output: 3 (Explanation: Window 'B.A' at indices 3-5 contains A and B. Signal indices are 3 and 5. Gap is 2, which is <= G. Length 3.)