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

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());
        List<Integer> list = getDivisor(getGcd(a, b));
        System.out.println(list.get(list.size() - k));
    }

    // 公約数
    private static List<Integer> getDivisor(int n) {
        List<Integer> list = new ArrayList<>();
        for (int i = 1; i <= n; i++) {
            if (n % i == 0) {
                list.add(i);
            }
        }
        return list;
    }

    // 最大公約数
    private static int getGcd(int x, int y) {
        return y == 0 ? x : getGcd(y, x % y);
    }
}
/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