import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	a, b = getlist()
	ans = (b ** 3 - a ** 3) / 3 - ((a + b) / 2) * (b ** 2 - a ** 2) + a * b * (b - a)
	print(-ans) 
	




if __name__ == '__main__':
	main()