Need Formula for Sum of Lowest 3 in list of 5 Random Cell Numbers

I have a list of numbers in J8 - J21 and L8 - L21. I need to be able to select any 5 and have the formula sum the lowest three. For example, a sum formula I have is =SUM(L18,L14,L15,J12,J15). I need to be able to convert that formula so that it will sum the lowest three numbers in those corresponding cells. I know how to do sum of lowest/highest in a sequential cell like A1:A10 but not when they are random like that. Any thoughts?