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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        sc.close();

        ArrayList<Integer> list = new ArrayList<>();

        for (int i = 1; i <= 100; i++) {
            if (a % i == 0 && b % i == 0) {
                list.add(i);
            }
        }
        System.out.println(list.get(list.size() - k));
    }
}
/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