unit_system = {
    "長度": {
        "米": 1,
        "千米": 1000,
        "厘米": 0.01,
        "英寸": 0.0254,
        "英尺": 0.3048
    },
    "溫度": {
        "攝氏度": lambda c: c,
        "華氏度": lambda c: c * 9/5 + 32,
        "開爾文": lambda c: c + 273.15
    }
}

def convert(value, from_unit, to_unit):
    # 遍歷所有單位類型
    for category in unit_system:
        units = unit_system[category]
        
        if from_unit in units and to_unit in units:
            # 處理特殊溫度轉換
            if category == "溫度":
                if from_unit == "華氏度":
                    c = (value - 32) * 5/9
                else:
                    c = value
                return units[to_unit](c)
            
            # 處理線性轉換
            base_value = value * units[from_unit]
            return base_value / units[to_unit]
    
    raise ValueError("不兼容的單位類型")

def parse_input(user_input):
    try:
        parts = user_input.split()
        value = float(parts[0])
        from_unit = parts[1].lower()
        to_unit = parts[3].lower()
        return value, from_unit, to_unit
    except:
        raise ValueError("輸入格式錯誤，示例：'5 km to m'")

def main():
    while True:
        try:
            user_input = input("單位轉換器 > ")
            if user_input.lower() == "exit":
                break
                
            value, from_unit, to_unit = parse_input(user_input)
            result = convert(value, from_unit, to_unit)
            print(f"{value} {from_unit} = {result:.4f} {to_unit}")
            
        except Exception as e:
            print(f"錯誤：{str(e)}")

unit_system["體積"] = {
    "升": 1,
    "毫升": 0.001,
    "立方米": 1000,
    "加侖": 3.78541
}