class Program {

	private int fib(int $n) {
		int $last = 0;
		int $cur = 1;
		--$n;
		while($n > 0) {
			--$n;
			int $tmp = $cur;
			$cur = $last + $cur;
			$last = $tmp;
		}
		return $cur;
	}

	public int main() {
		var_dump($this->fib(43));
	}
}