a=int(input())
b=int(input())
n=b-a+1
c=0
t=0
m=0
if a%2==0:
n=n-1
for i in range(n//2):
t=t+2
c=a+t
m=m+c
print(m+a)
elif a%2==1:
a=a+1
for i in range(n//2-1):
t=t+2
c=a+t
m=m+c
print(m+a)

a = int(input())
b = int(input())
if a%2 == 1 :
a += 1
if b%2 == 1 :
b -= 1
ans = ( (a + b) * ( ( b - a ) / 2 + 1 ) ) / 2
print(ans)

a=int(input())
b=int(input())
sum=0
for i in range(a,b+1):
if i%2==0: sum=sum+i
print(sum)