Given a list of intervals A and one interval B, find the least

number of intervals from A that can fully cover B.

If cannot find any result, just return 0;

For example:

Given A=[[0,3],[3,4],[4,6],[2,7]] B=[0,6] return 2 since we can use [0,3] [2,7] to cover the B

Given A=[[0,3],[4,7]] B=[0,6] return 0 since we cannot find any interval combination from A to cover the B