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带用户界面的计算器----可以计算加法，减法，乘法和除法，但是不能计算

带括号的四则运算，运行时，依次输入一个两位数、运算符号和第二个两位数,

就能输出计算结果,例如：计算65+79，依次输入"65"、“+”、"85",但是该

程序如果要计算一位数，必须输入两个数字，如果要输入8，必须输入08才行

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- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~ ---- calculator with a user interface can be calculated addition, subtraction, multiplication and division, but can not be calculated　the four fundamental operations with brackets, runs, Enter a digit in turn, operation symbols and the second two digits　can output results, such as: calculation of 65+79, followed by enter " 65 " ," +" ,"　85" , but the　program if To calculate a number, you must enter two numbers, if you want to enter the 8, you must enter 08 Caixing　~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~