#This program doesn't work with "ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-mswin32]"
#But it's OK with "ruby 1.9.1p0"


f=lambda{|x|
    return 1 if x<=1
    f[x-1]*x
  }
puts f[1000]




END {
    puts 'Now Exiting'       #This won't be excuted.And NO Error Message will be printed out, either.
}