GPA Calculator

Time limit1sMemory limit512 MB

Summary

Given a string of concatenated letter grades such as A+ and B, print the arithmetic mean of their grade points.

Level: Easy2 of 10
Topics: String, Implementation
Solved: No attempts yet

Problem

Jonghyun is building a program with Yeongdo that pulls data from the school portal and calculates Jonghyun's own grade points. Jonghyun wants to print the average grade point using the grade data Yeongdo extracted from the site.

The grade points for each grade follow this table.


Grade	Points
A+	4.5
A	4.0
B+	3.5
B	3.0
C+	2.5
C	2.0
D+	1.5
D	1.0
F	0.0

Input

The first line contains a string $S$ of the grades for each course. There are no separators between grades. The string consists only of characters from the table above, and its length is at most $1\,000$ .

Output

Print the arithmetic mean of the grade points for the grades listed in $S$ on the first line. An answer is accepted if its absolute or relative error is at most $10^{-4}$ .

Examples3

Example 1
Input
```
A+A
```
Expected output
```
4.25
```
Example 2
Input
```
A+AB+B+C
```
Expected output
```
3.5
```
Example 3
Input
```
CA+ABBB+A
```
Expected output
```
3.42857
```