Problem1881--Mike and Geometry Problem

1881: Mike and Geometry Problem

Time Limit: 2 Sec  Memory Limit: 256 MB
Submit: 0  Solved: 0
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Description

time limit per test
3 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Mike wants to prepare for IMO but he doesn't know geometry, so his teacher gave him an interesting geometry problem. Let's define f([l,r])=r-l+1 to be the number of integer points in the segment [l,r] with l≤r (say that ). You are given two integers n and k and n closed intervals [li,ri] on OX axis and you have to find:

In other words, you should find the sum of the number of integer points in the intersection of any k of the segments.

As the answer may be very large, output it modulo 1000000007 (109+7).

Mike can't solve this problem so he needs your help. You will help him, won't you?

Input

The first line contains two integers n and k (1≤k≤n≤200000)− the number of segments and the number of segments in intersection groups respectively.

Then n lines follow, the i-th line contains two integers li,ri (-109≤li≤ri≤109), describing i-th segment bounds.

Output

Print one integer number− the answer to Mike's problem modulo 1000000007 (109+7) in the only line.

Examples
Input
3 2
1 2
1 3
2 3
Output
5
Input
3 3
1 3
1 3
1 3
Output
3
Input
3 1
1 2
2 3
3 4
Output
6
Note

In the first example:

;

;

.

So the answer is 2+1+2=5.

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