apply Or.intro_right
case mp.seq_skip
T : Stmt
s : State
⊢ (∃ S' t, (Stmt.skip, s) ⇒ (S', t) ∧ (T, s) = (S'; T, t)) ∨ Stmt.skip = Stmt.skip ∧ (T, s) = (T, s)
case mp.seq_skip.h
T : Stmt
s : State
⊢ Stmt.skip = Stmt.skip ∧ (T, s) = (T, s)