The table below shows the number of girls who ran certain distance.
-------------|---|----|---|----|----|--Distance(Km) | 5 | 10 |15 | 20 | 25 |
-------------|---|----|---|----|----|--No. of girls | 2 | 1 | 3 | 4 | X |
-------------|---|----|---|----|----|-- Given that the median is 20Km, find the largest possible value of X