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BALKAN-SL 2019 G8

    Given an acute triangle ABC,(c)A B C,(c) is circumcircle with center OO and HH the orthocenter of the triangle ABCA B C. The line AOA O intersects (c)(c) at the point DD. Let D1,D2D_{1}, D_{2} and H2,H3H_{2}, H_{3} be the symmetrical points of the points DD and HH with respect to the lines AB,ACA B, A C respectively. Let (c1)\left(c_{1}\right) be the circumcircle of the triangle AD1D2A D_{1} D_{2}. Suppose that the line AHA H intersects again (c1)\left(c_{1}\right) at the point UU, the line H2H3H_{2} H_{3} intersects the segment D1D2D_{1} D_{2} at the point K1K_{1} and the line DH3D H_{3} intersects the segment UD2U D_{2} at the point L1L_{1}. Prove that one of the intersection points of the circumcircles of the triangles D1K1H2D_{1} K_{1} H_{2} and UDL1U D L_{1} lies on the line K1L1K_{1} L_{1}.

    Dataset text NuminaMath olympiads. Quoted with source.

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