#include <stdio.h>
#include<math.h>
int main() {
   int a,sum = 0,m = 1;
    int temp = 0;
    int k = 1;//1+2+2+3+3+3=14    1 = 1*1;2 = 2*2 3 = 3*3;
   scanf("%d",&a);
    for(int i = 1;i<=a;i++)
    {
       for(int j = 1;j<=i;j++)
       {
         if(k>a)break;
         sum+=i;
         k++;
       }

    }
    printf("%d",sum);
}