include

include

include

include

using namespace std;
struct BigNum
{
int len, s[9999];
BigNum()
{
memset(s, 0, sizeof(s));
len = 1;
}
BigNum operator = (const char* num)
{
len = strlen(num);
for (int i = 0; i < len; ++i)
s[i] = num[len-i-1] - '0';
return *this;
}
BigNum operator = (const int num)
{
char a[9999];
sprintf(a, "%d", num);
*this = a;
return *this;
}
BigNum (const int num)
{
this = num;
}
BigNum (const char num)
{
*this = num;
}
BigNum operator + (const BigNum &a)
{
BigNum c;
c.len = max(len, a.len) + 1;
for (int i = 0, x = 0; i < c.len; ++i)
{
c.s[i] = s[i] + a.s[i] + x;
x = c.s[i] / 10;
c.s[i] = c.s[i] % 10;
}
if(c.s[c.len-1] == 0)
--c.len;
return c;
}
BigNum operator * (const BigNum &x)
{
BigNum c;
c.len = len + x.len;
for (int i = 0; i < len; ++i)
for (int j = 0; j < x.len; ++j)
{
c.s[i+j] += s[i] * x.s[j];
c.s[i+j+1] += c.s[i+j] / 10;
c.s[i+j] %= 10;
}
if(c.s[c.len-1] == 0)
--c.len;
return c;
}
};
ostream& operator << (ostream &out, const BigNum &x)
{
for (int i = x.len - 1; i >= 0; --i)
cout << x.s[i];
return out;
}
istream& operator >> (istream &in, BigNum &x)
{
char num[9999];
in >> num;
x = num;
return in;
}
int main()
{
int n;
BigNum ans = 0, num = 1;
cin >> n;
for (int i = 1; i <= n; i++)
{
num = num * i;
ans = ans + num;
}
cout << ans << endl;
return 0;
}