
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int A = scan.nextInt();
		int B = scan.nextInt();
		int K = scan.nextInt();
		
		List<Integer> list = new ArrayList<>();
		for (int i = 1; i <= A; i++) {
			if ((A % i == 0) && (B % i == 0)) {
				list.add(i);
			}
		}
		
		System.out.println(list.get(list.size() - K));
		
		scan.close();
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz