#include<bits/stdc++.h>
using namespace std;
struct bigint{
	int len,a[110];
	int &operator[](int i)
	{
		return a[i];
	}
	bigint(int x=0){
		memset(a,0,sizeof(a));
		for(int len=1;x;len++)
			a[len]=x%10,x/=10;
		len--;
	}
	void flatten(int l)
	{
		len=l;
		for(int i=1;i<=len;i++)
			a[i+1]+=a[i]/10,a[i]=a[i]%10;
		while(a[len]) len--;
	}
	void print()
	{
		for(int i=max(len,1);i>=1;i--)
			cout<<a[i];
	}
	bigint operator+(bigint a,bigint b)
	{
		bigint c;
		c.len=max(a.len,b.len);
		for(int i=1;i<=c.len;i++)
			c[i]+=a[i]+b[i];
		c.flatten(c.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(2*len);
		return c;
	}
};
int main()
{
	bigint ans(0),fac(0);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		fac=fac*i;
		ans=ans+fac;
	}
	ans.print();
	return 0;
}

注：信息是
[Error] 'bigint bigint::operator+(bigint, bigint)' must take either zero or one argument

[Error] 'bigint bigint::operator*(bigint, int)' must take either zero or one argument