(VAR y x z)
(RULES
   +(0,y) -> y
   +(s(0),y) -> s(y)
   +(+(x,y),z) -> +(x,+(y,z))
   +(x,y) -> +(y,x)
   s(s(x)) -> s(x)
   s(x) -> s(s(x))
)
(COMMENT Example 24 of Aoto/Toyama, FSCD 2016)