代码：

#include <bits/stdc++.h>

using namespace std; 


struct BigInteger
{
	static const int BASE = 100000000;
	static const int WIDTH = 8;
	vector <int> s;
	long long len;

    BigInteger operator * (const BigInteger& b) 
	{
        BigInteger c; 
		c.len = len + b.len;
        for(int i = 0; i < len; i++)
        {
		    for(int j = 0; j < b.len; j++)
            {
                c.s[i+j] += s[i] * b.s[j];```
            }
		}
};

记录 [：]https://www.luogu.com.cn/record/73852383