四十分qaq

#include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
int A[1020];
int mul[1020];
void BIGcin(string s,int a[])
{
    int la = s.length();
    for (int i = 1;i <= la;i++)
    {
        a[i] =  s[la - i] - '0';
    }
    a[0] = la;
}

void BIGcout(int a[])
{
    int len = a[0];
    for (int i = len;i >= 1;i--)
    {
        cout << a[i] ;
    }
    cout << endl;
}
void BIGmul(int a[],int b,int mul[])
{
    int la = a[0];
    int len = la;
    int u = 0;
    for(int i = 1;i <= len;i++)
    {
        int t = (a[i] * b + u);
        mul[i] = t % 10;
        u = t / 10;
    }
    while(u > 0)
    {
        len++;
        mul[len] = u % 10;
        u /= 10;
    }
    mul[0] = len;
}
int main()
{
    string a;
    int b;
    cin >> a >> b;
    BIGcin(a,A);
    BIGmul(A,b,mul);
    BIGcout(mul);
    return 0;
}