import heapq
N, M, X = map(int, input().split())
Problem = [[] for _ in range(M)]
for _ in range(N):
    A, B = map(int, input().split())
    Problem[B - 1].append(A)
for i in range(M): Problem[i].sort()
Problem.sort(key = lambda x: x[-1] if x else -1001001001)
K = int(input())
C = list(map(int, input().split()))
CCnt = [0] * (N + 1)
for c in C: CCnt[c] += 1
Ans = 0
Score = 0
Used = []
for i in range(1, N + 1):
    if not Used or Problem and Problem[-1] and -Used[0] < X + Problem[-1][-1]:
        Score += X + Problem[-1].pop()
        for k in Problem.pop(): heapq.heappush(Used, -k)
    else:
        Score += -heapq.heappop(Used)
    Ans += Score * CCnt[i]
print(Ans)