Can't upgrade from 13.10 to 14.04

[Amine Sehili]

I'm having this message when I try to upgarde from 13.10 to 14.0

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

Thank you

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubuntu-release-upgrader-core 1:0.205.6
ProcVersionSignature: Ubuntu 3.11.0-20.35-generic 3.11.10.6
Uname: Linux 3.11.0-20-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
CrashDB: ubuntu
Date: Thu May 8 10:18:45 2014
InstallationDate: Installed on 2012-10-28 (556 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to saucy on 2014-05-08 (0 days ago)
VarLogDistupgradeTermlog: