I have a drive with this configuration:

fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x000f1b8b

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2612    20971520   83  Linux
/dev/sda3           60736       60801      525312   82  Linux swap / Solaris

There is 478GB unallocated space, how would I go about adding this space to /dev/sda1 without losing the data that is currently on /dev/sda1? (the filesystem is ext4) The OS is debian 6. Thank you in advance. :)