n, m = map(int, input().split()); assert 1 <= n <= 10**6 and 1 <= m <= 10**9
AB = [list(map(int, input().split())) for _ in range(n)]
for i in range(n): assert 0 <= AB[i][0] <= m and 1 <= AB[i][1] <= 10**9
C = [(m-AB[i][0]) // AB[i][1] + 1 for i in range(n)]
C.sort()
l = 0
r = n
while r - l > 1:
    mid = (l + r) >> 1
    f = 1
    for i in range(n):
        if i // mid + 1 > C[i]:
            f = 0
    if not f:
        l = mid
    else:
        r = mid

print(r)