let R be the TRS under consideration

f(_1,_2,f(_3,_4,_5)) -> f(f(_1,_2,_3),_4,f(_1,_2,_5)) is in elim_R(R)
let l be the left-hand side and r be the right-hand side of this rule
let p = epsilon
let theta = {}
let theta' = {_1/f(_1,_2,_3), _2/_4, _3/_1, _4/_2, _5/_5}
we have r|p = f(f(_1,_2,_3),_4,f(_1,_2,_5)) and
theta'(theta(l)) = theta(r|p)
so, theta(l) = f(_1,_2,f(_3,_4,_5)) is non-terminating w.r.t. R

Termination disproved by the forward process
proof stopped at iteration i=0, depth k=0
1 rule(s) generated