startNum, endNum = map(int, input().split())
sum = 0
cnt = 0

for i in range(1, endNum + 1):
	for j in range(1, i + 1):
		cnt += 1
		if(cnt >= startNum and cnt <= endNum):
			sum += i
	if cnt >= endNum:
		break
print(sum)
#### 잘하셨네 ~ 고생하셨어요 ,,,  : 그만잘해라 질투난다 :2
c4b29c3740802d91cb8ab711044b702c9e321a1d
<mask token>

<mask token>
for i in range(1, endNum + 1):
    for j in range(1, i + 1):
        cnt += 1
        if cnt >= startNum and cnt <= endNum:
            sum += i
    if cnt >= endNum:
        break
print(sum)

startNum, endNum = map(int, input().split())
sum = 0
cnt = 0
for i in range(1, endNum + 1):
    for j in range(1, i + 1):
        cnt += 1
        if cnt >= startNum and cnt <= endNum:
            sum += i
    if cnt >= endNum:
        break
print(sum)

startNum, endNum = map(int, input().split())
sum = 0
cnt = 0

for i in range(1, endNum + 1):
	for j in range(1, i + 1):
		cnt += 1
		if(cnt >= startNum and cnt <= endNum):
			sum += i
	if cnt >= endNum:
		break
print(sum)
#### 잘하셨네 ~ 고생하셨어요 ,,,  : 그만잘해라 질투난다 :2