from sys import stdin
from heapq import heappush, heappop

n, m, x, *indata = map(int, stdin.read().split())
offset = 0
hq = []
for i in range(n):
    s, t = indata[offset + 2*i],indata[offset + 2*i+1]
    heappush(hq, (-(s+x),t,0))

used = [0 for i in range(m+1)]
manzoku = [0]
while hq:
    score, janru, appeared = heappop(hq)
    score = -score
    if (appeared == 0) & (used[janru] >= 1):
        heappush(hq,(-score+x,janru,1))
    else:
        kari = manzoku[-1] + score
        used[janru] += 1
        manzoku.append(kari)

ans = 0
offset += n * 2
k = indata[offset]
for i in range(1,k+1):
    ans += manzoku[indata[offset+i]]
print("{}".format(ans))