n = int(input())
s = list(map(int,input().split()))
floor = []
floor.append(s)
for _ in range(n-1):
    x,y = map(int,input().split())
    flag = False
    for item in floor:
        if (x-item[0])**2 +(y-item[1])**2 >=400:
            flag = True
        else:
            break
    if flag == True:
        floor.append([x,y])
print(len(floor))