from heapq import heappop,heappush,heapify
from collections import defaultdict
N,M,X = map(int,input().split())
ab = []
dic = defaultdict(list)
for _ in range(N):
    a,b = map(int,input().split())
    ab.append((a,b))
    dic[b].append(a)
K = int(input())
C = list(map(int,input().split()))
q = []
for key in dic.keys():
    tmp = dic[key]
    tmp_q = []
    for i in range(len(tmp)):
        heappush(tmp_q,-tmp[i])
        
    x = -heappop(tmp_q)
    heappush(q,-(x+X))
    while tmp_q:
        x = -heappop(tmp_q)
        heappush(q,-x)
memo = []
while q:
    x = -heappop(q)
    memo.append(x) 
for i in range(N-1):
    memo[i+1] += memo[i]
ans = 0
for i in range(K):
    c = C[i]
    if c == 0:
        continue
    ans += memo[c-1]
print(ans)