FFFFFFFF
F
F                                   i
FFFFFFFF                                             t
F                                   i    sssssss   ttttttt
F              qqqq    u    u   i    s                t
F              q    q   u    u   i    sssssss        t
F              q    q   u    u   i            s        t
                qqqq   uuuuu   i    ssssss         tttt
                     q                   
                     q
                     q