#include<bits/stdc++.h>
using namespace std;
struct bigint {
	int size;
	vector<int> a;
	bool re;
	bigint() {
		a.clear(),size=0,re=1;
	}
	void operator=(string s) {
		a.clear();
		if (s[0]=='-') {
			re=0,size=s.size()-1;
			for (int i=s.size()-1,j=0; i; i--,j++)a.push_back(s[i]^48);
		} else {
			re=1,size=s.size();
			for (int i=s.size()-1,j=0; i>=0; i--,j++)a.push_back(s[i]^48);
		}
		if(s=="0")size=0;
		return;
	}
	bigint(long long n) {
		string s=to_string(n);
		a.clear();
		if (s[0]=='-') {
			re=0,size=s.size()-1;
			for (int i=s.size()-1,j=0; i; i--,j++)a.push_back(s[i]^48);
		} else {
			re=1,size=s.size();
			for (int i=s.size()-1,j=0; i>=0; i--,j++)a.push_back(s[i]^48);
		}
		if(s=="0")size=0;
		return;
	}
	bool operator==(bigint b) {
		if (re!=b.re)return 0;
		if (size!=b.size)return 0;
		for (int i=0; i<size; i++)if (a[i]!=b.a[i])return 0;
		return 1;
	}
	bool operator!=(bigint b) {
		if (re!=b.re)return 1;
		if (size!=b.size)return 1;
		for (int i=0; i<size; i++)if (a[i]!=b.a[i])return 1;
		return 0;
	}
	bool operator<(bigint b) {
		if (re!=b.re)return re<b.re;
		if (size!=b.size)return size<b.size;
		for (int i=size-1; i>=0; i--)if (a[i]!=b.a[i])return a[i]<b.a[i];
		return 0;
	}
	bool operator<=(bigint b) {
		if (re!=b.re)return re<b.re;
		if (size!=b.size)return size<b.size;
		for (int i=size-1; i>=0; i--)if (a[i]!=b.a[i])return a[i]<b.a[i];
		return 1;
	}
	bool operator>(bigint b) {
		if (re!=b.re)return re>b.re;
		if (size!=b.size)return size>b.size;
		for (int i=size-1; i>=0; i--)if (a[i]!=b.a[i])return a[i]>b.a[i];
		return 0;
	}
	bool operator>=(bigint b) {
		if (re!=b.re)return re>b.re;
		if (size!=b.size)return size>b.size;
		for (int i=size-1; i>=0; i--)if (a[i]!=b.a[i])return a[i]>b.a[i];
		return 1;
	}
	bigint operator+(bigint b) {
		bigint c;
		if (re&&b.re) {
			c.size=max(size,b.size);
			for (int i=0; i<min(size,b.size); i++) c.a.push_back(a[i]+b.a[i]);
			if (size>b.size) for (int i=b.size; i<size; i++)c.a.push_back(a[i]);
			else for (int i=size; i<b.size; i++)c.a.push_back(b.a[i]);
			for (int i=1; i<c.size; i++) c.a[i]+=c.a[i-1]/10,c.a[i-1]%=10;
			if(c.size)if (c.a[c.size-1]>9) c.a.push_back(1),c.a[c.size-1]%=10,c.size++;
			return c;
		} else if (!re&&!b.re) {
			c.size=max(size,b.size);
			for (int i=0; i<min(size,b.size); i++) c.a.push_back(a[i]+b.a[i]);
			if (size>b.size) for (int i=b.size; i<size; i++)c.a.push_back(a[i]);
			else for (int i=size; i<b.size; i++)c.a.push_back(b.a[i]);
			for (int i=1; i<c.size; i++) c.a[i]+=c.a[i-1]/10,c.a[i-1]%=10;
			if(c.size)if (c.a[c.size-1]>9)c.a.push_back(1),c.a[c.size-1]%=10,c.size++;
			c.re=0;
			return c;
		}
	}
	void operator+=(bigint b) {
		*this=*this+b;
		return;
	}
	bigint operator-(bigint b) {
		bigint c;
		if (re&&!b.re) {
			c.size=max(size,b.size);
			for (int i=0; i<min(size,b.size); i++) c.a.push_back(a[i]+b.a[i]);
			if (size>b.size) for (int i=b.size; i<size; i++)c.a.push_back(a[i]);
			else for (int i=size; i<b.size; i++)c.a.push_back(b.a[i]);
			for (int i=1; i<c.size; i++) c.a[i]+=c.a[i-1]/10,c.a[i-1]%=10;
			if(c.size)if (c.a[c.size-1]>9) c.a.push_back(1),c.a[c.size-1]%=10,c.size++;
			return c;
		}
		if (!re&&b.re) {
			c.size=max(size,b.size);
			for (int i=0; i<min(size,b.size); i++) c.a.push_back(a[i]+b.a[i]);
			if (size>b.size) for (int i=b.size; i<size; i++)c.a.push_back(a[i]);
			else for (int i=size; i<b.size; i++)c.a.push_back(b.a[i]);
			for (int i=1; i<c.size; i++) c.a[i]+=c.a[i-1]/10,c.a[i-1]%=10;
			if(c.size)if (c.a[c.size-1]>9)c.a.push_back(1),c.a[c.size-1]%=10,c.size++;
			c.re=0;
			return c;
		}
		if (re&&b.re) {
			if (*this >= b) {
				c.size = max(size, b.size);
				for (int i=0;i<c.size;i++)c.a.push_back(0);
				for (int i = 0; i < c.size; i++) {c.a[i] += a[i] - b.a[i]; if (c.a[i] < 0)c.a[i + 1]--, c.a[i] += 10;
				}
				for (int i = 0; i <= c.size + 10; i++) c.a[i + 1] += c.a[i] / 10,c.a[i] %= 10;
				for (; !c.a[c.size - 1] && c.size;)c.size--;
				return c;
			} else {
				c.size = max(size, b.size),c = b - *this,c.re = 0;return c;
			}
		}
		re=1,b.re=1,c=b-*this,re=0,b.re=0;
		return c;
	}
	bigint operator*(bigint b) {
		bigint c,zero;
		zero="0";
		if (*this==zero||b==zero)return zero;
		if (!(re^b.re)) {
			c.size=size+b.size;
			for (int i=0; i<c.size; i++) c.a.push_back(0);
			for (int i=0; i<size; i++) for (int j=0; j<b.size; j++) c.a[i+j]+=a[i]*b.a[j];
			for (int i=0; i<c.size-1; i++) c.a[i+1]+=c.a[i]/10,c.a[i]%=10;
			if (c.a[c.size-1]==0) c.size--;
			return c;
		}
		c.size=size+b.size,c.re=0;
		for (int i=0; i<c.size; i++) c.a.push_back(0);
		for (int i=0; i<size; i++) for (int j=0; j<b.size; j++) c.a[i+j]+=a[i]*b.a[j];
		for (int i=0; i<c.size-1; i++) c.a[i+1]+=c.a[i]/10,c.a[i]%=10;
		if (c.a[c.size-1]==0) c.size--;
		return c;
	}
	void operator*=(bigint b) {
		*this=*this*b;
		return;
	}
	bigint operator/(bigint b) {

	}
};
istream& operator>>(istream &inp,bigint &n) {
	string s;
	inp>>s;
	if (s[0]=='-') {
		n.re=0,n.size=s.size()-1;
		for (int i=s.size()-1,j=0; i; i--,j++)n.a.push_back(s[i]^48);
	} else {
		n.re=1,n.size=s.size();
		for (int i=s.size()-1,j=0; i>=0; i--,j++)n.a.push_back(s[i]^48);
	}
	if(s=="0")n.size=0;
	return inp;
}
ostream& operator<<(ostream &out,bigint n) {
	if (n.size==0)return putchar('0'),out;
	if (n.re==0)putchar('-');
	for (int i=n.size-1; i>=0; i--) {
		putchar(n.a[i]+48);
	}
	return out;
}
bigint i=1,sum;
int n;
int main() {
    freopen("factorial.in","r",stdin),freopen("factorial.out","w",stdout);
	cin>>n;
	for (int j=1;j<=n;j++){
		bigint k=j;
		i*=k,sum+=i;
	}
	cout<<sum;
	return 0;
}