  The PPSZ algorithm by Paturi, Pudl\'ak, Saks, and Zane [1998] is the fastest
known algorithm for Unique k-SAT, where the input formula does not have more
than one satisfying assignment. For k>=5 the same bounds hold for general
k-SAT. We show that this is also the case for k=3,4, using a slightly modified
PPSZ algorithm. We do the analysis by defining a cost for satisfiable CNF
formulas, which we prove to decrease in each PPSZ step by a certain amount.
This improves our previous best bounds with Moser and Scheder [2011] for 3-SAT
to O(1.308^n) and for 4-SAT to O(1.469^n).
