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BALKAN-SL 2012 G4

    Let MM be the point of intersection of the diagonals of a cyclic quadrilateral ABCDABCD . Let I1I_1 and I2I_2 are the incenters of triangles AMDAMD and BMCBMC , respectively, and let LL be the point of intersection of the lines DI1DI_1 and CI2CI_2 . The foot of the perpendicular from the midpoint TT of I1I2I_1I_2 to CLCL is NN , and FF is the midpoint of TNTN . Let GG and JJ be the points of intersection of the line LFLF with I1NI_1N and I1I2I_1I_2 , respectively. Let O1O_1 be the circumcenter of triangle LI1JLI_1J , and let Γ1\Gamma_1 and Γ2\Gamma_2 be the circles with diameters O1LO_1L and O1JO_1J , respectively. Let VV and SS be the second points of intersection of I1O1I_1O_1 with Γ1\Gamma_1 and Γ2\Gamma_2 , respectively. If KK is point where the circles Γ1\Gamma_1 and Γ2\Gamma_2 meet again, prove that KK is the circumcenter of the triangle SVGSVG .

    Dataset text AI-MO AoPS. Quoted with source.

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