Repeated Substring Search

Problem Statement: Given a string \( S \) and an integer \( k \), determine whether there exists a substring of length \( k \) that appears at least twice in \( S \). In other words, if there is any contiguous sequence of characters with length \( k \) that occurs two or more times within \( S \), output YES; otherwise, output NO.

Example: For \( S = "abcabc" \) and \( k = 3 \), the substring "abc" appears twice, so the answer is YES.

Note: If \( S \) is empty or its length is less than \( k \), then no such substring exists and the output should be NO.

inputFormat

Input Format:

• The input is given via stdin as two lines.
• The first line contains the non-empty string \( S \). The string consists of lowercase English letters and has no spaces.
• The second line contains an integer \( k \) representing the length of the substring to look for.

outputFormat

Output Format:

• Print YES to stdout if there exists a substring of length \( k \) in \( S \) that appears at least twice.
• Otherwise, print NO.

abcabc
3

YES