Total Coins Calculation

You are given a series of tasks numbered from 1 to n. Completing the i^th task grants you i coins. Given three integers n, i, and j (where tasks are 1-indexed), calculate the total number of coins earned when completing tasks from the i^th task to the j^th task inclusive.

You can calculate the sum of consecutive natural numbers using the formula:

$$S = \frac{j(j+1)}{2} - \frac{(i-1)i}{2}$$

Note that the input n represents the total number of tasks but it is not directly used in the calculation, other than to indicate the upper bound of tasks.

inputFormat

The input is read from standard input and consists of a single line containing three space-separated integers:

• n - the total number of tasks (1-indexed)
• i - the starting task index
• j - the ending task index

outputFormat

Output a single integer representing the total number of coins earned by completing tasks from the i^th task to the j^th task. The result should be printed to standard output.

5 2 4

9