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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    }
} 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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    }
} 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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int count = 0;
        int[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    } 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[] comd = new int[Math.min(a,b)]; comd new int[Math.min(a,b)] Math.min(a,b) Math.min Math a b for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        } int i = 1; int i = 1; i 1 i <= Math.min(a,b) i Math.min(a,b) Math.min Math a b i++ i++ i {
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        } {
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        } if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            } a%i == 0 && b%i == 0 a%i == 0 a%i a i 0 b%i == 0 b%i b i 0 {
                comd[count] = i;
                count++;
            } comd[count] = i comd[count] comd count i count++ count System.out.print(comd[count-k]) System.out.print System.out System System.out comd[count-k] comd count-k count k 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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    }
} 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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    }
} 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[] comd = new int[Math.min(a,b)];
        for(int i = 1; i <= Math.min(a,b); i++){
            if(a%i == 0 && b%i == 0){
                comd[count] = i;
                count++;
            }
        }
        System.out.print(comd[count-k]);
    }
}