/*#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("Hello world!\n");
return 0;
}
*/
/*#include<stdio.h>
int main()
{
double a,b,c,d;
scanf ("%lf %lf",&a, &b);
c = (a-100)*0.9;
d = (b-c)*100/c;
if (d<=10)
{
printf("정상");
}
else if(d<=20)
{
printf("과체중");
}
else
{
printf("비만");
}
}*/
/*#include<stdio.h>
int main()
{
double a,b,c,d,e;
scanf("%lf %lf",&a,&b);
if (a<150)
{
c = (a-100);
}
else if(a<160)
{
c = ((a-150)/2+50);
}
else
{
c = ((a-100)*0.9);
}
c = (b-c)*100/c;
if(c<=10)
{
printf("정상");
}
else if(c<=20)
{
printf("과체중");
}
else
{
printf("비만");
}
return 0;
}
*/
/*&#include<stdio.h>
int main() {
int n, i;
scanf("%d", &n);
for(i=0; i<n; i++) {
printf("%d ", i);
}
}*/
/*#include<stdio.h>
int main()
{
int i;
for (i=1; i<=100; i++)
{
printf("%d ",i);
}
}*/
/*#include<stdio.h>
int main()
{ int i,n;
scanf("%d",&n);
for (i=1; i<=n; i++)
{
printf("%d ",i);
}
}
*/
/*#include<stdio.h>
int main()
{
int a,b,i;
scanf("%d %d",&a,&b);
if (a<b)
{
for (i=a; i<=b; i++){
printf("%d ",i);
}
}
else if(a>=b)
{
for (i=b; i<=a; i++)
{
printf("%d ",i);
}
}
}*/
/*#include<stdio.h>
int main()
{char a,b,i;
scanf("%c %c",&a,&b);
for (i=a; i<=b; i++)
{
printf("%c ",i);
}
}*/
int main()
{
int i,n,sum;
scanf("%d",&n);
sum = 0;
for (i=1; i<=n; i++){
sum=sum+i;
}printf("%d",sum);
}