It is known that 13 plums are equal to the weight of 2 apples and 1 peach, and 4 plums and 1 apple are equal to the weight of 1 peach. How many plums weigh the same as 1 apple.
已知13个李子等于2个苹果和1个桃子的重量，而4个李子和1个苹果等于1个桃子的重量．多少个李子与1个苹果一样重．
<result>3</result>