# Roman to Integer

Convert a Roman numeral string to an integer.

Roman numerals: I=1, V=5, X=10, L=50, C=100, D=500, M=1000

Subtractive notation: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900

## Function Signature

```python
def roman_to_int(s: str) -> int:
```

## Parameters
- `s` — a valid Roman numeral string (1 to 3999)

## Returns
- The integer value

## Examples

```
roman_to_int("III") -> 3
roman_to_int("LVIII") -> 58
roman_to_int("MCMXCIV") -> 1994
```
