#include"stdio.h"
intmyf(intm){
return(1+m)*m>>1;
}

#include<stdio.h>
int total(int n)
{int i,s=0;
for(i=1;i<=n;i++)
s+=i;
return s;
}
int main()
{
int n;
scanf("%d",&n);
printf("%d\n",total(n));
return 0;
}