#!/usr/koeki/bin/ruby
#coding: euc-jp

srand()

m = Array.new
n = 100000
k = 20
for i in 0..n
  x = rand(k).to_f / k
  y = rand(k).to_f / k
  # p [x,y]
  r = x ** 2 + y ** 2
  if r < 1
    m << r
  end
end

p pi = (m.length.to_f / n) * 4