def find_last_one(arr):
    low, high = 0, len(arr) - 1
    result = -1  # Initialize result to -1, in case there are no 1s in the array

    while low <= high:
        mid = (low + high) // 2

        if arr[mid] == 1:
            result = mid  # Update the result and continue searching on the right side
            low = mid + 1
        else:
            high = mid - 1  # Search on the left side

    return result

# Example usage
arr = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
index_of_last_one = find_last_one(arr)

print("Index of the last occurrence of 1:", index_of_last_one)

def find_first_one(arr):
    low, high = 0, len(arr) - 1
    result = len(arr) - 1  # Initialize result to -1, in case there are no 1s in the array

    while low <= high:
        mid = (low + high) // 2

        if arr[mid] == 1:
            result = mid  # Update the result and continue searching on the left side
            high = mid - 1
        else:
            low = mid + 1  # Search on the right side

    return result

# Example usage
arr = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
index_of_first_one = find_first_one(arr)

print("Index of the first occurrence of 1:", index_of_first_one)