Using | x y | ≤ p {\displaystyle |xy|\leq p} , we know y {\displaystyle y} only consists of instances of a {\displaystyle a} . Moreover, because | y | ≥ 1 {\displaystyle |y|\geq 1} , it contains at least one instance of the letter a {\displaystyle a} .
Condition 3 => condition 2, pumping up leads to contradiction.