Enter a width:  10
Enter a height: 4

Here is your box:
+ + + + + + + + + +
+ + + + + + + + + +
+ + + + + + + + + +
+ + + + + + + + + +

Enter a width:  8
Enter a height: 5
Filled (y/n):   n

Here is your box:
+ + + + + + + +
+             +
+             +
+             +
+ + + + + + + +