How many days after coming upon the battlefield of Yanghe did Wang Zhen's army decide to turn back?
return Wang Zhen 's army coming upon the  battlefield of Yanghe ;return Wang Zhen 's army decides to turn back ;return day of #1 ;return day of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']