3.3. Find all pairs of natural numbers $x$ and $y$, such that $x! + 3 = y^2$.

 untranslated text remains in its original form.
3.3. 1. method. The square of a natural number can end with one of the digits $0,1,4,5,6$ and 9. $x!+3$ ends with the digit 3 if $x \geq 5$. The solutions are pairs (1,2), (3,3).