Patterns

First, check for block size of partition:
dumpe2fs /dev/hda1|grep 'Block size:'

Then do a filesystem check (resize2fs will not work without it):
e2fsck -f /dev/hda1
Expect it to take some time to run… (depends on partition size)

Make sure that you calculate the block size correctly. df shows the block size as each block=1024.
resize2fs /dev/hda1 36250000

Then use fdisk to delete the partition and recreate it with the new size. The newly freed space is then available to you in order to create a second partition.