#include <bits/stdc++.h>
using namespace std;


int main()
{
	int a, b;
	cin >> a >> b;

	double ans = 0;
	double d = 0.000001;
	for( double x = a; x <= b; x += d ) {
		ans -= (x * x - a * x - b * x + a * b) * d;
	}

	cout << fixed << setprecision(12) << ans << endl;
}