m = int(input())
res = []
ans = 0
b = ""
for i in range(m):
    b = input()
    c = b.split()
    list1 = [int(i) for i in c]
    res.append(list1)
n = int(input())
for i in range(m):
    if len(res[i]) > n:
        ans += (res[i][n - 1] * res[i][-1]) / 100
    else:
        ans += 1
print(ans)