發送短信 : Modeling a stacking yard transportation system

 __   _      ___     ______    _    _    _____    
| || | ||   / _ \\  |      \\ | || | || |  __ \\  
| '--' ||  / //\ \\ |  --  // | || | || | |  \ || 
| .--. || |  ___  |||  --  \\ | \\_/ || | |__/ || 
|_|| |_|| |_||  |_|||______//  \____//  |_____//  
`-`  `-`  `-`   `-` `------`    `---`    -----`