import sys
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N = I()

area = [[[] for _ in range(800)] for _ in range(800)]
XY = []
R = [-1,0,1]
ans = 0
for k in range(N):
    x,y = MI()
    XY.append((x,y))
    i = x//25
    j = y//25
    is_eliminated = 0
    for di in R:
        ni = i+di
        if not (0 <= ni < 800):
            continue
        for dj in R:
            nj = j+dj
            if not (0 <= nj < 800):
                continue
            for l in area[ni][nj]:
                xl,yl = XY[l]
                if (x-xl)**2+(y-yl)**2 < 400:
                    is_eliminated = 1
                    break
    if is_eliminated:
        continue
    else:
        area[i][j].append(k)
        ans += 1

print(ans)