There are three cards with 3, 4, and 5 written on them. Take two cards at random and add the two numbers on the cards, how many different sums can be obtained?
有三张卡片，上面分别写着3、4、5．从中任取两张卡片，把卡片上的两个数相加，可以得到多少个不同的和．
<result>3</result>