/* An input validation loop - with while */

#include <stdio.h>

int main(void) {
  int number;

  /* First prompt */
  printf("Enter a non-negative integer: ");
  scanf("%d", &number);

  /* Additional prompts if needed */
  while (number < 0) {
    printf("A *NON-NEGATIVE NUMBER* - Try again: ");
    scanf("%d", &number);
  }

  /* Printing the result */
  printf("Here it is: %d\n", number);
 
  return 0;
}