  We study the first-order finite-temperature electroweak phase transition of
the SU(2) gauge-Higgs model defined on a 4-dimensional isotropic lattice with
temporal extension N_t=2. Finite-size scaling study of Lee-Yang zeros yields
the value of the Higgs self coupling of the endpoint at lambda_c=0.00116(16).
An independent analysis of Binder cumulant gives a consistent value for the
endpoint. Combined with our zero-temperature measurement of Higgs and W boson
masses, this leads to M_{H,c}=73.3 +- 6.4 GeV for the critical Higgs boson mass
beyond which the electroweak transition turns into a crossover.
