(VAR x y u v)
(RULES
minus(x, x) -> 0
minus(x, y) -> cond(min(x, y) = y, x, y)
cond(TRUE, x, y) -> 1 + minus(x, y+1)
min(u, v) -> if(u < v, u, v)
if(TRUE, u, v) -> u
if(FALSE, u, v) -> v
)