---

n = int(inputC))

items=D

for - in range(n):
4
P, d = map(int, input().split())

net = p - d

items. append((d, net))
7
S= int(inputO))
8
items.sort(reverse=True)
9
res = 0
10
total = 0
11
for d, net in items:
12
if total + net <= S:
13
total += net
14
res += d
15
print(res)