Annie is practicing for the AP calculus exam in a few weeks. One problem in calculus is finding the area under the graph between two points ~a~ and ~b \ (a \le b)~ of a function (above the ~x~-axis only). While she knows how to solve this problem for many different functions, Annie is stumped by functions of the form ~f(x)=mx~. Given a function of that form, and integer points ~a~ and ~b~, can you solve the problem?

Constraints

For all subtasks,

~1 \le m \le 10~

~0 \le a \le b \le 100~

~m, a, b \in \mathbb{Z}~

Subtask 1 [33%]

~a = b~

Subtask 2 [33%]

~a = 0~

Subtask 3 [34%]

No additional constraints.

Input Specification

The first line of input will contain ~m~. The second will contain ~a~, and the third will contain ~b~.

Output Specification

Output the area under the graph between the two points ~a~ and ~b~ of the function ~f(x)=mx~. Output exactly to one decimal place, even if the area is an integer. For example, an answer of ~8~ should be output as ~8.0~.

Sample Input 1

2
1
3

Sample Output 1

8.0

Explanation for Sample Output 1

The graph of ~f(x)=2x~ (red) and the area under the graph between ~1~ and ~3~ (green) is shown as follows:

The area is ~8.0~.

Sample Input 2

9
99
99

Sample Output 2

0.0

Sample Input 3

3
2
3

Sample Output 3

7.5