U r1 r2

U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2
U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2
U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2U r1 r2