ค้นหา ID ของผู้ใช้ที่ติดตามโดย Mary และ Susan
Find the id of users who are followed by Mary and Susan.
follows_df = pd.DataFrame(columns=['f1', 'f2']); user_profiles_df = pd.DataFrame(columns=['uid', 'name'])
follows_df[follows_df['f2'].isin(user_profiles_df[(user_profiles_df['name'] == "Mary") | (user_profiles_df['name'] == "Susan")]['uid'])]['f1']