import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
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 <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-k));
	}
} import java.util.ArrayList; ArrayList java.util import java.util.HashMap; HashMap java.util import java.util.HashSet; HashSet java.util import java.util.Map; Map 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 <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-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();
		ArrayList<Integer> ans = new ArrayList<>();
		for(int i=1 ; i <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-k));
	} 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 <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-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 ArrayList<Integer> ans = new ArrayList<>(); ans new ArrayList<>() for(int i=1 ; i <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		} int i=1 ; int i=1 ; i 1 i <= 100 i 100 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 System.out.println(ans.get(ans.size()-k)) System.out.println System.out System System.out ans.get(ans.size()-k) ans.get ans ans.size()-k ans.size() ans.size ans 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();
		ArrayList<Integer> ans = new ArrayList<>();
		for(int i=1 ; i <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-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();
		ArrayList<Integer> ans = new ArrayList<>();
		for(int i=1 ; i <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-k));
	}
} Main
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
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 <= 100 ; i++) {
			if(a%i == 0 && b%i ==0) {
				ans.add(i);
			}
		}
		System.out.println(ans.get(ans.size()-k));
	}
}
