计算24游戏，最终要求是输入四个一位数，通过加减乘除，允许加入括号，计算出24，显示计算过程，并提示成功信息。可以首先完成输入三个一位数,只通过加减，计算出12；再完成通过加减乘除，再完成可以加入括号-Calculation of the 24 games, the final requirement to enter the four-digit, by addition, subtraction, multiplication and division, allowed to join the brackets calculated 24 show the calculation process, and prompt success information. Can enter three-digit first complete, only by adding or subtracting calculated 12　then completed by addition, subtraction, multiplication and division, and then complete the brackets can be added