#include<iostream>
#define Max 100005
using namespace std;
__int64 a[Max];
void calc()
{
__int64 i;//i 一定要用64,因为i*i*i,会爆的
for(i =1; i <= 100000; i++)
{
if(i % 3 == 0)
a[i] = a[i-1] + i*i*i;
else
a[i] = a[i-1] + i;
}
}
int main()
{
calc();
int n;
while(scanf("%d", &n) != EOF && n >= 0)
printf("%I64d\n", a[n]);
return 0;
}