import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long A = sc.nextLong();
        long B = sc.nextLong();
        long K = sc.nextLong();
        sc.close();

        int count = 0;
        for (int i = 100; i>0; i--) {
            if (A%i == 0 && B%i == 0) {
                count++;
                if (count == K) {
                    System.out.println(i);
                    return;
                }
            }
        }

    }


}
/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