import java.util.*;
import java.util.stream.*;
import java.lang.*;
import java.io.*;

class Ideone {
  public static void main (String[] args) throws java.lang.Exception {
    int l = -1000000000, r = 1000000000;
    int res = IntStream.range(l, r+1).sum();
    System.out.println(res);
  }
}