1 #include<stdio.h>
 2 #include<cmath>
 3 #include<iostream>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<queue>
 7 using namespace std;
 8 int main ()
 9 {
10     long int n,i,sum;
11     while(scanf("%ld",&n)!=EOF)
12     { 
13      sum=0;
14      for(i=1;i<=n;i++)
15      {
16       sum+=i;
17      }
18      printf("%ld\n",sum);
19      printf("\n");
20     }
21 return 0;
22 }