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

int fib(int n);

int main(int argc, char *argv[]) {
	if (argc != 2) {
		fprintf(stderr, "usage: %s <number>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	int num = atoi(argv[1]);
	printf("fib(%d) = %d\n", num, fib(num));
}

int fib(int n) {
	if (n == 0) {
		return 0;
	} else if (n == 1) {
		return 1;
	} else {
		return fib(n - 1) + fib(n - 2);
	}
}