import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int A = Integer.parseInt(sc.next());
        int B = Integer.parseInt(sc.next());
        int K = Integer.parseInt(sc.next());
        sc.close();
        int mas[] = new int[100];
        int sum = 1;
        for (int i = 100; i > 0; i--) {
            if (A % i == 0 && B % i == 0) {
                mas[sum] = i;
                ++sum;
            }
        }
        System.out.println(mas[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