  Direct and mixing-induced CP-violating asymmetries in Bs -> K+K- decays are
measured for the first time using a data sample of pp collisions, corresponding
to an integrated luminosity of 1.0 fb^{-1}, collected with the LHCb detector at
a centre-of-mass energy of 7 TeV. The results are C_{KK} = 0.14 \pm 0.11 \pm
0.03 and S_{KK} = 0.30 \pm 0.12 \pm 0.04, where the first uncertainties are
statistical and the second systematic. The corresponding quantities are also
determined for B0 -> pi+pi- decays to be C_{pipi} = -0.38 \pm 0.15 \pm 0.02 and
S_{pipi} = -0.71 \pm 0.13 \pm 0.02, in good agreement with existing
measurements.
