Problem: You are given an two integers i and j such that i ≤ j.
Task is to find the sum of all integers from i to j (both inclusive).  

For example:
i = 3
j = 5
then sum from i to j will be 3+4+5 = 12  

Input:
Single line containing two space separated integers i and j.  

Output:
Print out the sum of integers from i to j (both inclusive).  

Constraints:
0 ≤ i ≤ 1000000000000000000 (10^18)
0 ≤ j ≤ 1000000000000000000 (10^18)
i ≤ j
Absolute difference between i and j can be upto 1000000000000000000 
i.e. |j-i| ≤ 1000000000000000000 (10^18)

Subtask 1: (50 points)
0 ≤ i ≤ 1000000
0 ≤ j ≤ 1000000
i ≤ j
Absolute difference between i and j can be upto 1000000 
i.e. |j-i| ≤ 1000000

Subtask 2: (50 points)
Original Constraints  

Hint:
Use mathematics instead of loop to find sum.
Use BigInteger class of Java for large number multiplication.

SAMPLE INPUT
99 1000000000000

SAMPLE OUTPUT
500000000000499999995149

Solution (in PYTHON):

Solution:
def rangesum(s):
    a,b=map(long,s.split())
    len=b-a+1
    s=(a+(b,b-1)[len%2])*int(len/2)+(0,b)[len%2]
    return s
print rangesum(raw_input())