Some students jointly pay to buy football. If 4 of them decide not to participate, the remaining students will each have to share an extra 1 yuan. When the actual payment was made, another 6 people withdrew, and each of the remaining people paid an additional 3 yuan. How many people originally agreed to buy football?
一些同学共同出钱买足球，如果其中4人后来决定不参加，余下的人就要每人多分担1元．当实际付款时，又有6人退出，最后余下的人，每人又多负担3元．原先同意买足球的是多少人？
<result>20</result>