How do I draw an empty rectangle given its width and height in C?

I will get tons of down votes eventually but I have literally been struggling with this logical exercise for hours and I would appreciate some help. Given the width and the height, the compiler should draw a rectangle.

I have therefore decided to make use of for loops, which look like the smartest way to do the job.

Here is the code I have been using:

#include <stdio.h>

main()

{

int width, height, b, a;

  printf("Please insert the value of the width.\n");
  scanf("%d", & width);

  printf("Please insert the value of the height.\n");
  scanf("%d", & height);

for (a = 0; a != height; a++) {

    // fill the width
    for (b = 0; b != width; b++ ) {

        if (a == 0) {
            printf("*");}

        else if (a == width-1) {
            printf("*");
        }

        else if (b == height-1) {
            printf("*");
        }

        else if (b == 0) {
            printf("*");
        }

        else {
            printf(" ");
        }}

    printf("\n");
   }
}

I feel like I am missing something, but this is so confusing. May someone please tell me why my code doesn't draw a rectangle?