https://itmanual.net/%ed%8c%8c%ec%9b%8c%ed%8f%ac%ec%9d%b8%ed%8a%b8-%eb%b9%a8%ea%b0%84%ec%a4%84-%ec%97%86%ec%95%a0%ea%b8%b0-ppt-%eb%b9%a8%ea%b0%84-%eb%b0%91%ec%a4%84-%ec%a7%80%ec%9a%b0%ea%b8%b0/