Let x0 of type ι be given.
Let x1 of type ι be given.
Apply minus_SNo_invol with
x1,
λ x2 x3 . SNoLt x2 (minus_SNo x0) leaving 2 subgoals.
The subproof is completed by applying H1.
Apply minus_SNo_Lt_contra with
x0,
minus_SNo x1 leaving 3 subgoals.
The subproof is completed by applying H0.
Apply SNo_minus_SNo with
x1.
The subproof is completed by applying H1.
The subproof is completed by applying H2.