package main

import . "fmt"

func main() {
	var a,b float64
	Scan(&a,&b)
	f:=func(x float64) float64 {
		return x*x*x/3-(a+b)*x*x/2+a*b*x
	}
	s:=f(b)-f(a)
	Printf("%.8f\n",s)
}