안녕하세요 셀레니움 하는중에 다음과 같은 오류가 발생하는데 너무 궁금합니다.

# -*- coding: utf-8 -*-
"""
Created on Sun May  5 20:44:38 2019
 
@author: Administrator
"""
# -*- coding: utf-8 -*-
"""
Created on Sun May  5 12:55:16 2019
 
@author: Administrator
"""
 
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from bs4 import BeautifulSoup
import time
 
 
num_of_pagedowns = 18# 페이지수
rank = 1 
 
 
 
driver = webdriver.Chrome('C:\chromedriver.exe')
 
driver.get('https://m.naver.com')
 
time.sleep(1)
 
# 처음 로드 해서 변수 A 까지
elem = driver.find_element_by_xpath('//*[@id="t21"]/div/button').click() #팝업창 클릭
elem = driver.find_element_by_xpath('//*[@id="MM_SEARCH_FAKE"]') #검색창 클릭
elem.click()
elem = driver.find_element_by_xpath('//*[@id="query"]')
elem.send_keys('박지성')
elem.send_keys(Keys.ENTER)
time.sleep(1)
 
# 두번째 부터 변수 B까지,쇼핑 더보기 내부 로직 시작
elem = driver.find_element_by_xpath('//*[@id="nx_query"]')
elem.clear()
elem.send_keys('남성청결제')
elem.send_keys(Keys.ENTER)
time.sleep(2)
elem = driver.find_element_by_xpath('//*[@id="ct"]/section[1]/div[2]/a').click()
 
for a in range(0,3):
 
    if a == 0:
 
        body = driver.find_element_by_xpath('/html/body')   
 
        while num_of_pagedowns:
            body.send_keys(Keys.PAGE_DOWN)
            time.sleep(0.5)
            num_of_pagedowns -= 1
 
 
        html  = driver.page_source
        soup =BeautifulSoup(html,'lxml')
        titles = soup.find_all('span', class_='_2rxlO_K3YY')
        for title in titles:
            rank += 1
            if title.get_text()=='신세계몰':
                print(str(rank)+"번째 : "+title.get_text())
                time.sleep(2)
    elif 0 < a:
        body = driver.find_element_by_xpath('/html/body')   
        elem = driver.find_element_by_xpath('//*[@id="content"]/div[5]/a[%d]'%(a+1)).click() #이부분 도움주셔서 감사합니다
        while num_of_pagedowns:
            body.send_keys(Keys.PAGE_DOWN)
            time.sleep(0.5)
            num_of_pagedowns -= 1
        time.sleep(2)
 
        html  = driver.page_source
        soup =BeautifulSoup(html,'lxml')
        titles = soup.find_all('span', class_='_2rxlO_K3YY')
        for title in titles:
            rank += 1
            if title.get_text() =='신세계몰':
                print(str(rank)+"번째 : "+title.get_text())
                elem = driver.find_element_by_xpath('//*[@="_2rxlO_K3YY"]/a[contains(@title)]').click()