BZOJ 1303: [CQOI2009] Median Plot

1303: [CQOI2009] Median Graph

Time Limit: 1 Sec  Memory Limit: 162 MB
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Description

Given a permutation from 1 to n, count how many consecutive subsequences of odd lengths in the permutation have a median of b. The median is the number in the middle after arranging all elements from small to large.

Input

The first row is two positive integers n and b, and the second row is a permutation of 1~n.

Output

Output an integer, the number of consecutive subsequences with median b.

Sample Input

7 4

5 7 2 4 3 1 6

Sample Output

4

HINT

The third example explanation: {4}, {7,2,4}, {5,7,2,4,3} and {5,7,2,4,3,1,6}
N<=100000

Source

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Because it is an arrangement of n, b will only appear once, b is recorded as 0, smaller than b is recorded as -1, larger than b is recorded as 1, and the number of sequences with a sum of 0 is calculated.