.right-box:nth-child(even){
	background:url(https://tkww-static.tkww.hk/special/bg1.png)no-repeat;
  	background-size: 100% 100%;
}
.right-box:nth-child(odd){
	background:url(https://tkww-static.tkww.hk/special/bg2.png)no-repeat;
  	background-size: 100% 100%;
}