import java.util.*;
import java.io.*;

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 num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    }
} import java.util.*; util.* java import java.io.*; io.* 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 num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    }
} 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 num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    } 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 num = 0; num 0 for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        } int i = Math.min(a,b); int i = Math.min(a,b); i Math.min(a,b) Math.min Math a b i >= 1 i 1 i-- i-- i {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        } {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        } if (a % i == 0 && b % i == 0)
                num++; a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 num++ num if (num == k)
                System.out.println(i); num == k num k System.out.println(i) System.out.println System.out System System.out i if(num == k)
                    break; num == k num k break; 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 num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    }
} 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 num = 0;
        for (int i = Math.min(a,b); i >= 1; i--) {
            if (a % i == 0 && b % i == 0)
                num++;
            if (num == k)
                System.out.println(i);
                if(num == k)
                    break;
        }
    }
} Main
import java.util.*;
import java.io.*;

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