diff --git a/app.py b/app.py
index cdacc57..d8a7719 100644
--- a/app.py
+++ b/app.py
@@ -1,4 +1,5 @@
 """This python file will do the AutoClass job."""
+import time
 
 from selenium import webdriver
 from selenium.common import TimeoutException
@@ -25,6 +26,10 @@ def driver_screenshot(locator, path):
     WebDriverWait(driver, 10).until(ec.presence_of_element_located(locator)).screenshot(path)
 
 
+def driver_get_text(locator):
+    return WebDriverWait(driver, 10).until(ec.presence_of_element_located(locator)).text
+
+
 def login():
     driver.get('https://course.fcu.edu.tw/')
     driver_send_keys((By.ID, "ctl00_Login1_UserName"), config.get("username"))
@@ -44,13 +49,23 @@ def auto_class(class_ids):
     driver_click((By.ID, "ctl00_MainContent_TabContainer1_tabSelected_Label3"))
     for class_id in class_ids:
         driver_send_keys((By.ID, "ctl00_MainContent_TabContainer1_tabSelected_tbSubID"), class_id)
-        try:
-            WebDriverWait(driver, 0.5).until(ec.presence_of_element_located((By.ID,
-                                                                             "//*[@id='ctl00_MainContent_TabContainer1_tabSelected_gvToDel']/tbody/tr[2]/td[1]/input")))
-            class_ids.remove(class_id)
-        except TimeoutException:
+
+        # query remain position
+        driver_click((By.XPATH,
+                      "//*[@id='ctl00_MainContent_TabContainer1_tabSelected_gvToAdd']/tbody/tr[2]/td[8]/input"))
+        time.sleep(0.5)
+        alert = driver.switch_to.alert
+        remain_pos = alert.text.strip('剩餘名額/開放名額：').split("/")[0]
+        alert.accept()
+
+        if not remain_pos == '0':
             driver_click((By.XPATH,
                           "//*[@id='ctl00_MainContent_TabContainer1_tabSelected_gvToAdd']/tbody/tr[2]/td[1]/input"))
+            if driver_get_text((By.XPATH, "//*[@id='ctl00_MainContent_TabContainer1_tabSelected_lblMsgBlock']/span")) == "加選成功":
+                print("成功加選課程：" + class_id)
+                class_ids.remove(class_id)
+        else:
+            pass
     auto_class(class_ids)