Two teammates each publish a roster of busy windows. Within one roster the windows are given sorted by start and never overlap each other. A window from the first roster and a window from the second overlap if they share a stretch of positive length (touching at a single endpoint does not count). Count the number of pairs (one window from each roster) that overlap.

Input format

Line 1: two integers n and m. Next n lines: two integers start end for roster A (sorted, non-overlapping). Next m lines: two integers start end for roster B (sorted, non-overlapping).

Output format

A single integer: the number of overlapping window pairs.

Constraints

• 1 ≤ n, m ≤ 100000
• 0 ≤ start < end ≤ 1000000
• Each roster is sorted by start and internally non-overlapping.

2 2
0 3
5 8
1 2
6 9

2

2 1
0 2
4 6
2 4

0