Goal:
  
  n1 : Z
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1' : n1 < n2
  H2' : n2 < n3
  T1 : V.lt x3 x3 -> V.lt x3 x3 -> V.lt x3 x3
  T2 : V.lt y1 y2 -> V.lt y2 y3 -> V.lt y1 y3
  T3 : n1 = n2 -> n2 = n3 -> n1 = n3
  ============================
   ((n2 = n3 -> n1 = n3) -> x3 = x3)


DEBUG:Going to execute:
intro; clear id
Level 4: evaluation returns
<coq-core.plugins.ltac::cut@0>
where
$1 := n2 = n3 -> n1 = n3
of type
constr of type tacvalue