from itertools import accumulate
from heapq import *

N,M,X = map(int,input().split())
D = {}

for _ in range(N):
  a,b = map(int,input().split())
  a = -a-X
  if b not in D:
    D[b] = [a]
  else:
    heappush(D[b],a)

K = int(input())
C = list(map(int,input().split()))
imos = [0]*(N+1)

for c in C:
  imos[0] += 1
  imos[c] -= 1

ac_imos = list(accumulate(imos))
E = []

for k,v in D.items():
  n = heappop(v)
  heappush(E,(n,k))

ans = 0

for c in ac_imos:
  if not E:
    break

  a,b = heappop(E)
  ans += -a*c
  
  if D[b]:
    d = heappop(D[b])
    d += X
    heappush(E,(d,b))

print(ans)