fp = ARGV[0]; sp = ARGV[1]; p = ARGV[2]
ff = File.new fp; sf = File.new sp, "w+"
fl = ff.readlines; l_n = fl.length
tl = (l_n*p).round
u = l_n - 1; l = u - tl
fl[l..u].each {|ln| sf.puts ln}