from collections import Counter

n, m = map(int, input().split())
D = []
for i in range(n):
    a, b = map(int, input().split())
    D.append((m - a) // b + 1)
D.sort()
# print(D)
left = 0
right = n
mid = (left + right) // 2
count = 0
while left < right:
    flag = True
    for i in range(n):
        max = i // mid + 1
        if max > D[i]:
            flag = False
            break
    if flag:
        right = mid
    else:
        left = mid + 1
    # print(mid, left, right, flag)
    mid = (left + right) // 2
    count += 1
    if count == 100:
        exit()
print(left)