#include<iostream>
using namespace std;
int n;
unsigned long long money(int m);
int day(int n);
int main(void)
{
    cin>>n;
    cout<<money(n);
    
}
int day(int n)
{	int sum=0;int a;
    for(int i=1;i<=n;i++)
    {
        if(sum+i>n)
        {
		a=i-1;break;}
        
        
           sum+=i; 
        
    }
    return a;
}
unsigned long long money(int m)
{
    unsigned long long money=0;int day1=day(n);
    for(int t=1;t<=day1;t++)
    {
        money+=t*t;
    }
    money=money+(n-(1+day1)*day1/2)*(day(n)+1);
    return money;
}