Let m be given.
We prove the intermediate claim Ln: SNo n.
An exact proof term for the current goal is ordinal_SNo n (nat_p_ordinal n (omega_nat_p n Hn)).
We prove the intermediate claim Lm: SNo m.
An exact proof term for the current goal is ordinal_SNo m (nat_p_ordinal m (omega_nat_p m Hm)).
rewrite the current goal using minus_add_SNo_distr n m Ln Lm (from right to left).
An exact proof term for the current goal is add_SNo_In_omega n Hn m Hm.