def mSrt(ary)
  p ary
  if (l=ary.size)>1 then
     mMrg(mSrt(ary.take(l/2)),mSrt(ary.drop(l/2)))
  else ary end
end
def mMrg(a1,a2)
  if a1.size==0 then a2
  elsif a2.size==0 then a1
  elsif a1[0]>a2[0] then a1[0,1]+mMrg(a1.drop(1),a2)
  else  a2[0,1]+mMrg(a1,a2.drop(1))
  end
end
def mMrg_t(a1,a2,r=[])
  if a1.size==0 then r+a2
  elsif a2.size==0 then r+a1
  elsif a1[0]>a2[0] then mMrg_t(a1.drop(1),a2,r+a1[0,1])
  else  mMrg_t(a1,a2.drop(1),r+a2[0,1])
  end
end