# Here your code !
MAX = 20000
CELL = 40
SEG = MAX.div(CELL) + 3
ZONE = SEG.times.map { SEG.times.map { [] } }

n = gets.to_i
coins = n.times.map { gets.split.map(&:to_i) }


puts coins.inject(0) {|s,c|
    cx, cy = c.map {|v| v / CELL + 1}
    nears = [cx - 1, cx, cx + 1].product([cy - 1, cy, cy + 1])
    intersect = nears.all? do |dx,dy|
        begin
        ZONE[dx][dy].empty? || ZONE[dx][dy].all? { |v| 2.times.inject(0) {|q,i| q + (c[i] - v[i]) ** 2} >= 400  }
        rescue
            p [dx,dy]
        end
    end

    unless intersect
        s
    else
        ZONE[cx][cy].push(c)
        s+1
    end
}