import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        double dif = (b - a) / 1000000.0;
        double ans = 0;
        for (double i = a; i < b; i += dif) {
            ans += (i - a) * (i - b) * dif;
        }
        System.out.println(Math.abs(ans));
    }
}