PROGRAMMING:Delete at most three characters
Given a string composed of all lowercase English letters, you are allowed to delete at most three characters. How many different strings are there?
###Input format:
Enter the string in the interval [4, $$10 ^ 6 $$] which is composed of all lowercase English letters in one line.
###Output format:
Output the number of different strings after deleting at most three characters in one line.
###Input example:
```in
ababcc
```
###Output example:
```out
twenty-five
```
**Tips:**
Delete 0 characters to get "ABCC".
Delete one character to get "babcc", "aabcc", "abbcc", "abacc" and "ababc".
Delete two characters to get "ABCC", "BBCC", "BACC", "babc", "AACC", "AABC", "abbc", "ABAC" and "ABAB".
Delete three characters to get "ABC", "BCC", "ACC", "BBC", "BAC", "bab", "AAC", "AAB", "ABB" and "ABA"< br>
answer：If there is no answer, please comment
###Input format:
Enter the string in the interval [4, $$10 ^ 6 $$] which is composed of all lowercase English letters in one line.
###Output format:
Output the number of different strings after deleting at most three characters in one line.
###Input example:
```in
ababcc
```
###Output example:
```out
twenty-five
```
**Tips:**
Delete 0 characters to get "ABCC".
Delete one character to get "babcc", "aabcc", "abbcc", "abacc" and "ababc".
Delete two characters to get "ABCC", "BBCC", "BACC", "babc", "AACC", "AABC", "abbc", "ABAC" and "ABAB".
Delete three characters to get "ABC", "BCC", "ACC", "BBC", "BAC", "bab", "AAC", "AAB", "ABB" and "ABA"< br>
answer：If there is no answer, please comment