555=6.515555=66.1155555=661...31555555=6613...635555555=66137...4755555555=661375...559个5=6613756...5110个5=66137566..11可以发现余数每增加6个5循环：51,11,31,63,47,55（1997-2）/6=332...3所以余数是63...