(VAR b1 b2 b3 x y )
(RULES 
        p(s(x)) -> x
        p(0) -> 0
        le(0, y) -> true
        le(s(x), 0) -> false
        le(s(x), s(y)) -> le(x, y)
        average(x, y) -> if(le(x, 0), le(y, 0), le(y, s(0)), le(y, s(s(0))), x, y)
        if(true, b1, b2, b3, x, y) -> if2(b1, b2, b3, x, y)
        if(false, b1, b2, b3, x, y) -> average(p(x), s(y))
        if2(true, b2, b3, x, y) -> 0
        if2(false, b2, b3, x, y) -> if3(b2, b3, x, y)
        if3(true, b3, x, y) -> 0
        if3(false, b3, x, y) -> if4(b3, x, y)
        if4(true, x, y) -> s(0)
        if4(false, x, y) -> average(s(x), p(p(y)))
        
)