Subarray Sum Equals K

Problem statement

An energy meter records signed changes. Count how many nonempty consecutive reporting windows have a total exactly equal to a given target k. Windows with different start or end positions count separately, even when their values match.

Input format

First line: n k. Second line: n integers.

Output format

Print the number of matching windows.

Constraints

1 <= n <= 100000; -10000 <= value <= 10000; -1000000000 <= k <= 1000000000; use 64-bit counts.

Sample input

5 3
1 2 1 2 3

Sample output

4