完全按照书里抄下来的，编译不通过

#include <bits/stdc++.h>
using namespace std;
#define MAXN 1000
struct Bigint
{
	int len, a[MAXN];
	Bigint(int x = 0)
	{
		memset(a,0,sizeof a);
		for(len=1;x;len++)
			a[len] = x%10, x/=10;
		len -- ;
	}
	int& operator[](int i)
	{
		return a[i];
	}
	void flatten(int L)
	{
		len = L;
		for(int i=1;i<=len;i++)
			a[i+1] += a[i]/10, a[i]%=10;
		for(;!a[len];) len--;
	}
	void print(){
		for(int i=max(len,1);i>=1;i--)
			printf("%d",a[i]);
	}
	Bigint operator+(Bigint a, Bigint b)
	{
		Bigint c;
		int len = max(a.len, b.len);
		for(int i=1;i<=len;i++)
			c[i] += a[i]+b[i];
		c.flatten(len+1);
		return c;	
	}
	Bigint operator*(Bigint a, int b)
	{
		Bigint c;
		int len = a.len;
		for(int i=1;i<=len;i++)
			c[i] = a[i]*b;
		c.flatten(len+11);
		return c;	
	}
};
int main()
{
	Bigint ans(0),fac(1);
	int m;
	cin>>m;
	for(int i=1;i<=m;i++)
	{
		fac = fac * i;
		ans = ans + fac;
	}
	ans.print();
}