The following predicates are all loop invariants:
L21: {input1 = div * y + x}
L22: {x >= 0}
L23: {y = input2}
Finally, we verify the segment,
{input1>0 and input2>0}
read(x); read(y);
div := 0;
{input1 = div * y + x;
x >= 0;
y = input2;}
This completes the correctness proof.