75分蒟蒻求助qwq

代码如下：

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
struct bi{
    public:
    int num[1000], len = 0;
    bi(string i = "0"){
        memset(num, 0, sizeof(num));
        for(int j = i.length() - 1; j >= 0; j--){
            num[i.length() - j] = i[j] - '0';
            len++;
        }
    }
    int leng(){
        return len;
    }
    void print(){
        for(int i = len; i >= 1; i--){
            cout << num[i];
        }
    }
    bi operator +(bi tee){
        int x = 0;
        bi t;
        int tlen = 0;
        for(int i = 1; i <= max(this->leng(), tee.leng()); i++){
            t.num[i] += x;
            t.num[i] += this->num[i] + tee.num[i];
            x = t.num[i] / 10;
            t.num[i] %= 10;
            tlen++;
        }
        if(x > 0){
            tlen++;
            t.num[tlen] = x;
        }
        t.len = tlen;
        return t;
    }
    bi operator *(int tee){
        int x = 0;
        bi t;
        int tlen = 0;
        for(int i = 1; i <= this->leng(); i++){
            t.num[i] += this->num[i] * tee;
            t.num[i] += x;
            x = t.num[i] / 10;
            t.num[i] %= 10;
            tlen++;
        }
        if(x > 0){
            tlen++;
            t.num[tlen] = x;
        }
        t.len = tlen;
        return t;
    }
};
int main(){
    int n;
    cin >> n;
    bi ans, cur("1");
    for(int i = 1; i <= n; i++){
        cur = (cur * i);
        ans = (ans + cur);
    }
    ans.print();
    cout << endl;
    return 0;
}