I don't know what to do. :-(

I can't install scotty or yesod.

$ cabal install scotty

cabal: Could not resolve dependencies:

trying: scotty-0.5.0 (user goal)

trying: base-4.7.0.0/installed-dc1... (dependency of scotty-0.5.0)

trying: wai-extra-1.3.4.6 (dependency of scotty-0.5.0)

trying: stringsearch-0.3.6.4 (dependency of wai-extra-1.3.4.6)

rejecting: stringsearch-0.3.6.4:-base3 (conflict:

base==4.7.0.0/installed-dc1..., stringsearch-0.3.6.4:base3 => base>=2 && <3)

rejecting: stringsearch-0.3.6.4:+base3 (conflict:

base==4.7.0.0/installed-dc1..., stringsearch-0.3.6.4:base3 => base>=3 && <4)

Backjump limit reached (change with --max-backjumps).