#include<bits/stdc++.h>
using namespace std;
long long factorial(int n)
{
	if(n==1|n==0)return 1;
	return factorial(n-1)*n;
}
long long factorial_sum(int n)
{
	long long sum=0;
	for(int i=1;i<=n;i++)sum+=factorial(i);
	return sum;
}
int main()
{
	int n;
	cin>>n;
	cout<<factorial_sum(n);
}

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