xxxxxxx  xxxxxx  xxxxxx  xxxxxxx
x                              x
x               s            e x
x          i        i          x
x                              x
x     xxxxxxxx    xxxxxxxx     x
x     x                  x     x
      x                e x      
      x     t  t   t     x      
x     x                  x     x
x     x     t      t     x     x
x  s  x                  x  s  x
x     x     t      t     x     x
x     x                  x     x
x           t      t           x
               c                
      t     t  c   t     t      
x                              x
x     x     t      t     x     x
x     x                  x     x
x  s  x     t      t     x  s  x
x     x                  x     x
x     x     t      t     x     x
      x                  x      
      x     t  t   t     x      
x     x                  x     x
x     x                  x     x
x     xxxxxxxx    xxxxxxxx     x
x                              x
x e        i    s   i          x
x                              x
xxxxxxx  xxxxxx  xxxxxx  xxxxxxx