Mountain Climbing Altitude Search

You are climbing a mountain and have recorded the altitudes at different checkpoints in a sorted list. Given a target altitude, write a program to find the closest altitude that is less than or equal to the target using binary search. Input Format: - The first line contains an integer m (1 <= m <= 1000), the number of checkpoints. - The second line contains m space-separated integers representing the altitudes in sorted order. - The third line contains an integer target representing the desired altitude. Output Format: - An integer representing the closest altitude less than or equal to target, or -1 if all altitudes are greater. Example: Input: 5 1000 1500 2000 2500 3000 1800 Output: 1500