Sum from a to b

You are given two integers $a$ and $b$ ($a \le b$). Find the sum of all integers from $a$ to $b$ inclusive.

A single line with two integers $a$ and $b$ ($-10^6 \le a \le b \le 10^6$).

A single integer — the sum.

Accumulate the sum with a for loop: start from $0$ and add the next number on each step. The sum reaches $5 \cdot 10^{11}$ — use long long in C++ and int64 in Go.

In the first example: $2 + 3 + 4 + 5 = 14$.