import java.util.*;

public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    }
} Main public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

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

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    } 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 div = 1; div 1 for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        } int i = Math.min(a, b); int i = Math.min(a, b); i Math.min(a, b) Math.min Math a b i >= 0 i 0 i-- i-- i {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        } {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        } if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            } a % i == 0 && b % i == 0 && --k == 0 a % i == 0 && b % i == 0 && --k == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 --k == 0 --k k 0 {
                div = i;
                break;
            } div = i div i break; System.out.println(div) System.out.println System.out System System.out div String args[] args public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    }
} public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        int div = 1;
        for (int i = Math.min(a, b); i >= 0; i--) {
            if (a % i == 0 && b % i == 0 && --k == 0) {
                div = i;
                break;
            }
        }

        System.out.println(div);
    }
}