  We present a measurement of the time-dependent charge-parity (CP) violation
parameters in B0 -> pi+ pi- decays. The results are obtained from the final
data sample containing 772 million BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We obtain the CP violation parameters Acp = +0.33 +/- 0.06 (stat) +/- 0.03
(syst) and Scp = -0.64 +/- 0.08 (stat) +/- 0.03 (syst), where Acp and Scp
represent the direct and mixing-induced CP asymmetry, respectively. Using an
isospin analysis including results from other Belle measurements, we find 23.8
< phi2 < 66.8 degrees is disfavored at the 1 sigma level, where phi2 is one of
the three interior angles of the CKM unitarity triangle related to B_{u,d}
decays.
