/*
使用递归计算1到n的和
*/
public class Test3
{
public static void main(String[] args){
java.util.Scanner s = new java.util.Scanner(System.in);
int n = s.nextInt();
int s = sum(n);
}
public static int sum(int n){
if(n == 1)
return 1;
return n = n + sum(n - 1);
}
}