Count subsequences of type a^i, b^j, c^k

Given a string S, return number of subsequences of the form aⁱb^jc^k, where i >= 1, j >=1 and k >= 1.

Note:

1. Two subsequences are considered different if the set of array indexes picked for the 2 subsequences are different.
2. For large test cases, the output value will be too large, return the answer MODULO 10^9+7

Input Format:

First parameter: string S

Output Format:

Returns the Number

Example 1:

Input:
s = "abbc"
Output: 3
Explanation: Subsequences are abc for 1st b, abc for 2nd b and abbc.

Example 2:

Input:
s = "abcabc"
Output: 7
Explanation: Subsequences are abc, abc,
abbc, aabc abcc, abc and abc.

Constraints:

• 1 <= |S| <= 10⁵
• Expected Time Complexity: O(Length of String).
• Expected Auxiliary Space: O(1)