Let $p$ and $q$ be positive integers satisfying $p < q$ and $p + q = k$ . What is the smallest value of $k$ that does not determine $p$ and $q$ uniquely?

Kepler. Discussing PYQs. Q.no. 55

Let ppp and qqq be positive integers satisfying p<qp < qp<q and p+q=kp + q = kp+q=k . What is the smallest value of kkk that does not determine ppp and qqq uniquely?