You don't show the chart. But whatever the parents, you need to set up a Punnett Square to find the answer.
Examples of output:
L - long
l - short
LL x ll will result in all Ll (long)
Ll x Ll will result in 1 LL (long), 2 Ll (long) and 1 ll (short)
ll x ll will result in all ll (short)
lots of combinations you can do