Xiaohua surrounds a triangle with matches of the same length. One match is used for the first side, 2 matches are used for the second side, and how many matches are needed for the third side.
小华用同样长的火柴围一个三角形，其中第一条边用了1根火柴，第二条边用了2根火柴，第三条边需要多少根火柴．
<result>2</result>