实现计算i的i次方的加和，i从1到n，其中n为用户输入的任意整数。（要考虑结果可能超出长整数long的表示范围的情况）-big integer, implented with C++. Functions include add and multiply.

输入两个大整数，整数长度可以很长，原则上没有长度限制，将这两个大整数进行相乘得出结果。-Enter the two big integers, integer length can be very long, in principle, there is no length limit, these two big integers multiplying the result.