def triangle_area(a, b, c):
    if a + b <= c or a + c <= b or b + c <= a:
        return -1 
    s = (a + b + c)/2    
    area = (s * (s - a) * (s - b) * (s - c)) ** 0.5
    area = round(area, 2)
    return area
from typing import List
def separate_paren_groups(paren_string: str) -> List[str]:
    result = []
    current_string = []
    current_depth = 0
    for c in paren_string:
        if c == '(':
            current_depth += 1
            current_string.append(c)
        elif c == ')':
            current_depth -= 1
            current_string.append(c)
            if current_depth == 0:
                result.append(''.join(current_string))
                current_string.clear()
    return result