n,d=map(int,input().split())
x=[]
y=[]
e=[]
flag=1
for i in range(n):
    xi,yi=map(int,input().split())
    x.append(xi);y.append(yi)
    if yi>d:
        flag=0
        break
if flag==0:
    print("无法覆盖")
else:
    for i in range(n-1):
        for j in range(i+1,n):
            if x[j]<x[i]:
                x[i],x[j]=x[j],x[i]
                y[i],y[j]=y[j],y[i]
    #print(x)
    #print(y)
    for i in range(n):
        flag=1
        if len(e)==0:
            ei=(d**2-y[i]**2)**0.5+x[i]
            e.append(ei)
        else:
            for tot in e:
                if (x[i]-tot)**2+y[i]**2<=d**2:
                    flag=0
                    break
            if flag==1:
                ei=(d**2-y[i]**2)**0.5+x[i]
                e.append(ei)
    ans=len(e)
    print(ans)
'''
3 5
6 3
-1 4
5 4
'''