#include <stdlib.h>
#include <stdio.h>

int main(void) {
  int n, next, count;
  int previous = 0;       /* Fibonacci 0 */
  int current = 1;	  /* Fibonacci 1 */

  printf("Calculate which Fibonacci number? ");
  scanf("%d",&n);
  /* before here, n has been set to the bound */
  count = 2;
  while (count <= n) {
    next = previous + current;	   // i.e. 2 = 0 + 1
    previous = current;
    current = next;		   // after: 2 + 1
    count++;
  }

  printf("Fibonacci %d is %d\n", n, current);
  return EXIT_SUCCESS;
}