Notice that the first n in the line "n = n+1;" is underlined? If you hover over that variable, you will see a Code Analyzer message that I believe will recommend not changing the value of the loop variable inside the loop. Any changes you make will persist only to the end of that iteration of the loop; when the next iteration starts the loop variable will take on the next value from the vector over which you're iterating.
fprintf("First, k is %d.\n", k)
fprintf("Next, k is %d.\n", k)
If you just mean to skip to the next value of n (from 1:iteration) then just eliminate that line.
If you mean to skip (from 1 to 3 at the next iteration, not running the body of the loop for n = 2) then you're going to need to switch to a while loop.
If you want to stop the loop entirely when or if L becomes 0, use break.