A sentence is a list of words that are separated by a single space with no leading or trailing spaces. Each of the words consists of only uppercase and lowercase English letters (no punctuation).

• For example, "Hello World", "HELLO", and "hello world hello world" are all sentences.

You are given a sentence s​​​​​​ and an integer k​​​​​​. You want to truncate s​​​​​​ such that it contains only the first k​​​​​​ words. Return s​​​​​​ after truncating it.

Example 1:

Input: s = "Hello how are you Contestant", k = 4
Output: "Hello how are you"
Explanation:
The words in s are ["Hello", "how" "are", "you", "Contestant"].
The first 4 words are ["Hello", "how", "are", "you"].
Hence, you should return "Hello how are you".

Example 2:

Input: s = "What is the solution to this problem", k = 4
Output: "What is the solution"
Explanation:
The words in s are ["What", "is" "the", "solution", "to", "this", "problem"].
The first 4 words are ["What", "is", "the", "solution"].
Hence, you should return "What is the solution".

Example 3:

Input: s = "chopper is not a tanuki", k = 5
Output: "chopper is not a tanuki"

Constraints:

• 1 <= s.length <= 500
• k is in the range [1, the number of words in s].
• s consist of only lowercase and uppercase English letters and spaces.
• The words in s are separated by a single space.
• There are no leading or trailing spaces.