Lens system configuration of OGLE-2017-BLG-1099. Notations are the same as those in Fig. 4, except that an additional inset (left) is presented to show a zoomed-in view of the central region. The source positions corresponding to t₁ and t₂ designated in Fig. 5 are marked by the empty magenta dots. The size of the dot in the main panel is arbitrary, but the dot in the left inset is scaled to the source size.