计算1！+2！+…+n!
递归方法

#include<iostream>
using namespace std;
int fac(int n);
int main()
{
	int n,n1=0,sum=0;
	cin >> n;
	for (int i = 0;i < n;i++)
	{
		n1 = fac(n);
		sum += n1;
	}
	cout << sum;
	return 0;

}
int fac(int n)
{
	if (n == 1 || n == 0)
	{
		return 1;
	}
	else
		return n * fac(n - 1);
}