tìm số6
999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999996999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999699999999999999999999999999999999999999999699999999999999999999999999999999999999999999999999699999999999999999999999999999999999999999999999999996999999999999999999999999999999999966699999999999999
có bao nhiêu số 6
có 8 số 6