N,M=map(int,input().split())
l=[]
for i in range(N):
    a,b=map(int,input().split())
    l.append((M-a)//b+1)
l.sort()
ok=N
ng=0
while ok-ng>1:
    mid=(ok+ng)//2
    flg=True
    for i in range(N):
        if i//mid>=l[i]:
            flg=False
    if flg:
        ok=mid
    else:
        ng=mid
print(ok)