While reading Pauli's Exclusion principal from here, they said that
The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers." Now again in we know that the The orbital angular momentum quantum number $l= 0,1,2... (n-1)$ – Source
So from here we can say that $l\neq n$. So here automatically no two electrons can have the same four quantum numbers. So what's new in Pauli's principle?