N, M = map(int, input().split())
AB = [tuple(map(int, input().split())) for _ in range(N)]
E = [(M - a) // b + 1 for a, b in AB]
E.sort()
ok = N
ng = 0
while ok - ng > 1:
    mid = (ok + ng) // 2
    F = []
    for i in range(N // mid + 1):
        for _ in range(mid):
            F.append(i + 1)
    if all(E[i] >= F[i] for i in range(N)):
        ok = mid
    else:
        ng = mid
print(ok)