请按照四则运算加、减、乘、除、幂（^）和括号的优先关系和惯例，编写计算器程序。要求：

（1）　　 从键盘输入一个完整的表达式，以回车作为表达式输入结束的标志。

（2）　　 输入表达式中的数值均为大于等于零的整数。中间的计算过程如果出现小数也只取整。

-Follow the four operations add, subtract, multiply, divide, power (^) and brackets the priority relations and practices, write calculator program. Requirements: (1) from the keyboard to enter a complete expression, in order to enter as a sign of the end of the expression entered. (2) Enter the expression values are greater than zero integer. Middle of the computation process only if there is a decimal rounded.