Analyze the functions of variables and statements in the program,

According to the sequence shown in the flow chart, we can see that:

The function of this program is to compare the function values of f(x)=2x+3 and g(x)=x2.

And outputs the maximum value.

Because the output h(a)=a2, then

2a+3≤a2, and the solution is a≤- 1 or a≥3.

The value range of ∴a is [3, +∞) ∨ (-∞,-1].

So the answer is: [3, +∞) ∨ (-∞,-1].