Failed to upgrade from 14.04 to 16.04

[Maxim Perenesenko]

The problem occures at the stage of calculation changes for the upgrade.

I have russian interface and therefore get russioan message, so here is google translation:

"Could not calculate the upgrade system

Detected an insoluble problem when calculating the upgrade.

  This may be due to the fact that:
  * Upgrading to Ubuntu pre-release
  * The use of the current pre-release version of Ubuntu
  * Unofficial software not provided by Ubuntu

If none of the above does not fit, please report this error with the command «ubuntu-bug ubuntu-release-upgrader-core» in the terminal."

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.13.0-92.139-generic 3.13.11-ckt39
Uname: Linux 3.13.0-92-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Fri Jul 29 12:54:11 2016
InstallationDate: Installed on 2014-03-15 (866 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-07-29 (0 days ago)
VarLogDistupgradeTermlog: