2+2==4. Itβs a bit boring, but hopefully the way was somehow enlightening. Anyhow, 2=π(π(0))2=S(S(0)) and 4=π(π(π(π(0))))4=S(S(S(S(0)))).
2+2=π(π(0))+π(π(0))βΉ2+2=S(S(0))+S(S(0))βΉ
2+2=π(π(π(0))+π(0))βΉ2+2=S(S(S(0))+S(0))βΉ
2+2=π(π(π(0))+1)βΉ2+2=S(S(S(0))+1)βΉ
2+2=π(π(π(π(0))))=4