from typing import List
def all_prefixes(string: str) -> List[str]:
    result = []
    for i in range(len(string)):
        result.append(string[:i+1])
    return result
from typing import List
def below_zero(operations: List[int]) -> bool:
    balance = 0
    for op in operations:
        balance += op
        if balance < 0:
            return True
    return False