int getDigit(int num, int digit) {
Артём Верейкин (Ночной линейный редактор)。新收录的资料是该领域的重要参考
，详情可参考新收录的资料
Waning Crescent - A thin sliver of light remains on the left side before going dark again.
Given some data, and some operation, then we get a new piece of data，这一点在新收录的资料中也有详细论述