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 and of a function (above the -axis only). While she knows how to solve this problem for many different functions, Annie is stumped by functions of the form . Given a function of that form, and integer points and , can you solve the problem?

#### Constraints

For all subtasks,

##### Subtask 1 [33%]

##### Subtask 2 [33%]

##### Subtask 3 [34%]

No additional constraints.

#### Input Specification

The first line of input will contain . The second will contain , and the third will contain .

#### Output Specification

Output the area under the graph between the two points and of the function . Output exactly to one decimal place, even if the area is an integer. For example, an answer of should be output as .

#### Sample Input 1

```
2
1
3
```

#### Sample Output 1

`8.0`

#### Explanation for Sample Output 1

The graph of (red) and the area under the graph between and (green) is shown as follows:

The area is .

#### Sample Input 2

```
9
99
99
```

#### Sample Output 2

`0.0`

#### Sample Input 3

```
3
2
3
```

#### Sample Output 3

`7.5`

## Comments