while (scanf(\"%ld %ld %ld\",&a,&b,&c) ==

while (scanf(\"%ld %ld %ld\",&a,&b,&c) ==
while (scanf(\"%ld %ld %ld\",&a,&b,&c) ==

while (scanf(\"%ld %ld %ld\",&a,&b,&c) ==
while（true）则执行
scanf()的返回意思项目数,==3的意思是有没有读取了三个变量
这段换合起来就是说,如果scanf读取到三个变量时则进行while循环