Given a string s and an integer k, reverse the first k characters for every 2k characters counting from the start of the string.

If there are fewer than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and leave the other as original.

Examples

Example 1

Input:  s = "abcdefg", k = 2
Output: "bacdfeg"

Example 2

Input:  s = "abcd", k = 2
Output: "bacd"

Constraints

• 1 <= s.length <= 10⁴
• s consists of only lowercase English letters.
• 1 <= k <= 10⁴