you give list segment al_1 ar_1 al_2 ar_2 dot al_n ar_n bl_1 br_1 bl_2 br_2 dot bl_n br_ninitially segment al_i ar_i equal l_1 r_1 segment bl_i br_i equal l_2 r_2in step choose segment second list extend 1 in word suppose you ve choose segment x y transform x 1 y x y 1lets define total intersection I sum length intersection correspond pair segment ie sumlimits_i1ntextintersection_lengthal_i ar_i bl_i br_i empty intersection length 0 length segment x y equal y xWhat minimum number step need I greater equal k