require 'Monitor'
 lock = Monitor.new
 count = 0;
 t1 = Thread.new do
 　100000.times do
 　　lock.synchronize do
 　　　count += 1
 　　end
 　end
 end
 t2 = Thread.new do
 　100000.times do
 　　lock.synchronize do
 　　　count += 1
 　　end
 　 end
 end
 t1.join; t2.join
 puts count