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 c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-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 c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-1));
	}
} Main public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-1));
	} main {

		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-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 c = sc.nextInt(); c sc.nextInt() sc.nextInt sc int d = a<b?a:b; d a<b?a:b a<b a b a b ArrayList<Integer> foo = new ArrayList<>(); foo new ArrayList<>() for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		} int i=1; int i=1; i 1 i<=d i d i++ i++ i {

			if(a%i==0 && b%i==0)
				foo.add(i);
		} {

			if(a%i==0 && b%i==0)
				foo.add(i);
		} if(a%i==0 && b%i==0)
				foo.add(i); a%i==0 && b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 foo.add(i) foo.add foo i Collections.sort(foo, Collections.reverseOrder()) Collections.sort Collections foo Collections.reverseOrder() Collections.reverseOrder Collections System.out.println(foo.get(c-1)) System.out.println System.out System System.out foo.get(c-1) foo.get foo c-1 c 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 c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-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 c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-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 c = sc.nextInt();

		int d = a<b?a:b;

		ArrayList<Integer> foo = new ArrayList<>();

		for(int i=1;i<=d;i++) {

			if(a%i==0 && b%i==0)
				foo.add(i);
		}
		Collections.sort(foo, Collections.reverseOrder());
		System.out.println(foo.get(c-1));
	}
}

