From man apt-get:

   -f, --fix-broken

       Fix; attempt to correct a system with broken dependencies in place. This

       option, when used with install/remove, can omit any packages to permit APT

       to deduce a likely solution. If packages are specified, these have to

       completely correct the problem. The option is sometimes necessary when

       running APT for the first time; APT itself does not allow broken package

       dependencies to exist on a system. It is possible that a system's dependency

       structure can be so corrupt as to require manual intervention (which usually

       means using dselect(1) or dpkg --remove to eliminate some of the offending

       packages). Use of this option together with -m may produce an error in some

       situations. Configuration Item: APT::Get::Fix-Broken.