说明：  本程序实现计算任意长整数的加法运算，大致过程为显示提示信息-->用户输入—>显示结果。 程序中字符集限定为’1’ ’2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’ ‘8’ ’9’ ‘0’ ’,’ ‘ ’ ,长整数的长度不予限制。 利用双向循环链表实现长整数的存储，每个结点含一个整型变量。任何整型变量的范围是-（215—1）~（215—1）。输入和输出形式：按中国对于长整数的表示习惯，每四位一组，组间用逗号隔开。
(This procedure to achieve the calculation of arbitrary length integer addition operations, generally the process to show message-> User input-> result will be displayed. Program character set limited to 1 2 3 4 5 6 7 8 9 0, , a long integer that does not limit the length. The use of two-way cycle to achieve a long list integer storage, each node contains an integer variable. The scope of any integer variables is- (215-1) ~ (215-1). Input and output forms: according to China s long habit of integers that each of four groups of groups separated by commas.)