import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.get(k-1));
      }
} import java.util.ArrayList; ArrayList java.util import java.util.Collections; Collections java.util import java.util.Scanner; Scanner 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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.get(k-1));
      } main {
    
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int k = sc.nextInt();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.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 ArrayList<Integer>ans  = new ArrayList<>(); ans new ArrayList<>() for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    } int i=1; int i=1; i 1 i<=Math.max(a,b) i Math.max(a,b) Math.max Math a b i++ i++ i {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    } {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    } if(a%i==0 && b%i==0) {
    		ans.add(i);
    	} a%i==0 && b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 {
    		ans.add(i);
    	} ans.add(i) ans.add ans i Collections.sort(ans,Collections.reverseOrder()) Collections.sort Collections ans Collections.reverseOrder() Collections.reverseOrder Collections System.out.println(ans.get(k-1)) System.out.println System.out System System.out ans.get(k-1) ans.get ans 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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.get(k-1));
      }
} Main
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
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();
    ArrayList<Integer>ans  = new ArrayList<>();
    
    for(int i=1; i<=Math.max(a,b); i++) {
    	if(a%i==0 && b%i==0) {
    		ans.add(i);
    	}
    }
    Collections.sort(ans,Collections.reverseOrder());
	System.out.println(ans.get(k-1));
      }
}
