python3 贪心
import math
n, d = map(int, input().split())
seg = []
failed = False
for i in range(n):
x, y = map(int, input().split())
if y > d:
failed = True
else:
len = (d*d - y*y)
len = math.sqrt(len)
seg.append([x-len, x+len])
if failed:
print("-1")
else:
seg.sort(key = lambda x:x[1])
res = 1
last = seg[0][1]
for i in range(n):
if seg[i][0] > last:
res += 1
last = seg[i][1]
print(res)