You are given 2 letters $a, b$. Count the number of letters in between $a$ and $b$ in the alphabet.
### Input
- 2 letters $a, b$.
### Output
- The number of letters in between $a$ and $b$ in the alphabet.
### Constraints
- $a, b$ is a letter in the alphabet, in either lowercase or uppercase.
### Example
Input:
```
a E
```
Output:
```
3
```
