Koizumi subtracted the sum of the upper digits of the four-digit number from a four-digit number, and the difference was a four-digit number of 604. So, what is the number represented by this mouth.
小泉用一个四位数减去这个四位数各位上数字之和，得到的差是一个四位数604口．那么，这个口代表的数字是多少．
<result>8</result>