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According to Ancient Ninjas, string making is a form of art. There are various methods of string making, one of them uses previously generated strings to make the new one. Suppose you have two strings A and B, to generate a new string C, you can pick a subsequence of characters from A and a subsequence of characters from B and then merge these two subsequences to form the new string.

Though while merging the two subsequences you cannot change the relative order of individual subsequences. What this means is - suppose there are two characters ‘Ai’ and ‘Aj’ in the subsequence chosen from ‘A’, where i < j, then after merging, if i acquires position k and j acquires p then k < p should be true and the same apply for subsequence from B.

Given strings ‘A’, ‘B’, ‘C’ can you count the number of ways to form string ‘C’ from the two strings ‘A’ and ‘B’ by the method described above? Two ways are different if any of the chosen subsequences is different.

As the answer could be large so return it after modulo 10 ^ 9 + 7.

For Example :

let A = a, B = ac, C = ac.

Now In this example, we can take whole string B to form C or take substring {a} and substring {c} from A and B, respectively to make C. Hence the answer is 2.

You are given an integer array 'arr' of size 'N' and an integer 'K'.

Your task is to find the total number of subarrays of the given array whose sum of elements is equal to k.

A subarray is defined as a contiguous block of elements in the array.

Example:

Input: ‘N’ = 4, ‘arr’ = [3, 1, 2, 4], 'K' = 6

Output: 2

Explanation: The subarrays that sum up to '6' are: [3, 1, 2], and [2, 4].

A ninja needs to complete ‘n’ tasks. Each task is represented by an uppercase letter of the English alphabet. Different letters are assigned to different tasks. A ninja can complete tasks in any order. He takes one unit of time to complete one task. For each unit of time, he could complete either one task or just be idle.

Ninja easily gets bored by doing the same task again. So he decided to keep at least ‘t’ units of time between any two same tasks.

You are given a string ‘tasks’ consisting of ‘n’ uppercase letters of the English alphabet, representing the tasks ninja need to complete, and an integer ‘t’ representing the least units of time between any two same tasks. Find out the minimum total units of time ninja will take to complete all ‘n’ tasks.

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