public class Main {
    public static void main(String[] args) {
        String s = "abcfdegh"; 
        int k = 2; 
 
        int maxLen = 1, start = 0, currLen = 1, currStart = 0;
 
        for (int i = 1; i < s.length(); i++) {
            if (Math.abs(s.charAt(i) - s.charAt(i - 1)) <= k) {
                currLen++;
            } else {
                currLen = 1;
                currStart = i;
            }
 
            if (currLen > maxLen) {
                maxLen = currLen;
                start = currStart;
            }
        }
 
        System.out.println(s.substring(start, start + maxLen));
    }
}
 

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