import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    }
} import java.util.*; util.* java public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc int k = sc.nextInt(); k sc.nextInt() sc.nextInt sc List<Integer> list = new ArrayList<>(); list new ArrayList<>() int min = Math.min(a,b); min Math.min(a,b) Math.min Math a b for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        } int i = 1; int i = 1; i 1 i<=min i min i++ i++ i {
            if (a % i == 0 && b % i == 0) list.add(i);
        } {
            if (a % i == 0 && b % i == 0) list.add(i);
        } if (a % i == 0 && b % i == 0) list.add(i); a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 list.add(i) list.add list i list.sort(Collections.reverseOrder()) list.sort list Collections.reverseOrder() Collections.reverseOrder Collections System.out.println(list.get(k - 1)) System.out.println System.out System System.out list.get(k - 1) list.get list k - 1 k 1 String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    }
} Main
import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int min = Math.min(a,b);
        for (int i = 1; i<=min;i++) {
            if (a % i == 0 && b % i == 0) list.add(i);
        }
        list.sort(Collections.reverseOrder());
        System.out.println(list.get(k - 1));
    }
}
