import sys
import heapq

input = sys.stdin.readline

jewels = []
bags = []

N, K = map(int, input().split())

for _ in range(N) :
    m, v = map(int, input().split())
    jewels.append((-v, m))

for _ in range(K) :
    bags.append(int(input()))
    
jewels.sort(key = lambda x: (x[1], x[0]))
bags.sort()

pq = []
ans = 0
idx = 0

for bag in bags :
    while idx < N and jewels[idx][1] <= bag :
        heapq.heappush(pq, jewels[idx][0])
        idx += 1
    
    if pq :
        cost = heapq.heappop(pq)
        ans -= cost

print(ans)