#include<stdio.h>
int main()
{
	int a, b;
	scanf("%d %d", &a, &b);
	printf("%.20lf\n", (a * a * a - b * b * b) / 3.0 - (a + b) * (a * a - b * b) / 2.0 + a * a * b - a * b * b);
	return 0;
}