21650_Sunscreen

To avoid unsightly burns while tanning, each of the C ( 1 ≤ C ≤ 2500 ) cows must cover her hide with sunscreen when they're at the beach. Cow i has a minimum and maximum SPF rating ( 1 ≤ minSPF_i ≤ 1,000; minSPF_i ≤ maxSPF_i ≤ 1,000 ) that will work. If the SPF rating is too low, the cow suffers sunburn; if the SPF rating is too high, the cow doesn't tan at all ........

The cows have a picnic basket with L ( 1 ≤ L ≤ 2500 ) bottles of sunscreen lotion, each bottle i with an SPF rating SPF_i ( 1 ≤ SPF_i ≤ 1,000 ). Lotion bottle i can cover cover_i cows with lotion. A cow may lotion from only one bottle.

What is the maximum number of cows that can protect themselves while tanning given the available lotions?

* Line 1:   Two space-separated integers: C and L

* Lines 2..C+1:   Line i describes cow i's lotion requires with two integers: minSPF_i and maxSPF_i

* Lines C+2..C+L+1:   Line i+C+1 describes a sunscreen lotion bottle i with space-separated integers: SPF_i and cover_i

A single line with an integer that is the maximum number of cows that can be protected while tanning.

3 2
3 10
2 5
1 5
6 2
4 1

2