# Here your code !
def d2(a,b)
    2.times.inject(0) do |s, i|
        s + (a[i] - b[i]) ** 2
    end
end

n = gets.to_i
coins = n.times.map {gets.split.map(&:to_i)}
areas = 100.times.map { Array.new(100) }

s = coins.inject(0) {|s,c|
    i,j = c.map {|v| v.div 200}
    areas[i][j] ||= []
    if areas[i][j].all? {|put| d2(put,c) >= 400}
        areas[i][j].push(c)
        s+1
    else
        s
    end
}

puts s