n,d=map(int,input().split())
#print(n,d)
p=[]
flag=True
for i in range(n):
   x,y=map(int,input().split())
   if abs(y)>d:
       flag=False
       break
   p.append([x-(d*d-y*y)**0.5,x+(d*d-y*y)**0.5])
if flag:
#    print('ok')
    for i in range(n-1):
        for j in range(i,n-1):
            if p[j][0]>p[j+1][0]:
                p[j+1],p[j]=p[j],p[j+1]
    tmp=p[0][1]
    ans=1
    for i in range(1,n):
        if p[i][0]>tmp:
            ans+=1
            tmp=p[i][1]
    print(ans)
else:
    print("无法覆盖")