# Most frequent substring problem.

Given a string, we want to know the maximum no. of occurrences of any substring that satisfies following two conditions:
1. The substring's lengths is within in inclusive range of `minLength` to `maxLength`.
2. The total no. of unique characters in the string doesn't exceed `maxUnique`.
For example, given a string s=abcde, minLength=2, maxLength=5, maxUnique=3, the substrings matching the criteria are (ab, bc, cd, de, abc, bcd, cde). Any shorter string fails he `minLength>=2` any longer will fail `maxUnique <= 3`. Each of the substring occurs only one time.
**INPUT :**
First line contains a string, second line contains minLength, third line contains maxLength, and the last line contains maxUnique.
**Constraints :**
- **2<=n<=10<sup>5</sup>**
- 2<=minLength<= maxLength <=26
- maxLength<n
- 2<=maxUnique<=26
**SAMPLE INPUT :**
ababab
2
3
4
**SAMPLE OUTPUT :**
3
**EXPLANATIONS : **
We want to find the no. of occurrences of the most frequently occurring substring of s= "ababab" that has the length in the inclusive range from minLength = 2 and maxLength=3 and contains maximum of maxUnique = 4 unique characters. The substring ab occurs three times aba, bab and ba occurs twice. Because we want maximum of this frequencies we return 3 as our answer.