N = gets.to_i
Ps = (0...N).map{ |i|
  x,y = gets.split.map &:to_f
  theta = Math.atan2(x,y)
  [theta,i,x,y]
}.sort

Ds = Ps + Ps

R2 = (0...N).map{ |k|
  t,i,x,y = Ds[k]
  v = [x,y]
  r = x**2 + y**2
  Ds[k+1..-1].each{ |t2,i2,x2,y2|
    break if i == i2
    v[0] += x2; v[1] += y2
    r = [r, v[0]**2 + v[1]**2].max
  }
  r
}.max

puts Math.sqrt(R2)
