books = []
count = 0
with open('input.txt') as file:
    n ,v , t =[int(i) for i in file.readline().split()]
    for i in range(n):
        x , y = [int(i) for i in file.readline().split('-')]
        books.append(int(x)*int(y))
books.sort()
symbols = v*t
for i in books:
    if symbols - i >= 0:
        count+=1
        symbols -=i
    else:
        break
print(count)