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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    }
} 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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    }
} 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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    } 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 int count = 0; count 0 int ans = 0; ans 0 int max = Math.max(a, b); max Math.max(a, b) Math.max Math a b for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        } int i = max; int i = max; i max i > 0 i 0 i-- i-- i {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        } {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        } if (a % i == 0 && b % i == 0) count++; a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 count++ count if (count == k) {
                ans = i;
                break;
            } count == k count k {
                ans = i;
                break;
            } ans = i ans i break; System.out.println(ans) System.out.println System.out System System.out ans 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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    }
} 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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    }
} 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();

        int count = 0;
        int ans = 0;
        int max = Math.max(a, b);
        for (int i = max; i > 0; i--) {
            if (a % i == 0 && b % i == 0) count++;

            if (count == k) {
                ans = i;
                break;
            }
        }

        System.out.println(ans);
    }
}
