#include<stdio.h>
int main()
{
int i,n,sum;
scanf("%d",&n);
if(n>0)
{
for (i=1;i<=n;i++)
{ sum=sum+i; }
printf("%d",sum);
}
if(n<0)
{
for (i=n;i<=1;i++)
{
sum=sum+i;}
printf("%d",sum);}
else if(n==0){ printf("not applicable");}
}