import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	}
}
 import java.util.ArrayList; ArrayList java.util import java.util.Collections; Collections java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	} main {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) List<Integer> list=new ArrayList<Integer>(); list new ArrayList<Integer>() 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 for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		} int i=1; int i=1; i 1 101>i 101 i i++ i++ i {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		} {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		} if(a%i==0&&b%i==0) {
				list.add(i);
			} a%i==0&&b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 {
				list.add(i);
			} list.add(i) list.add list i Collections.reverse(list) Collections.reverse Collections list System.out.println(list.get(k-1)) System.out.println System.out System System.out list.get(k-1) list.get list k-1 k 1 String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	}
} Main
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//List<String> list= new ArrayList<String>(Arrays.asList(s.split("")));
		List<Integer> list=new ArrayList<Integer>();
		//Integer[][] array = new Integer[n][m];
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i=1;101>i;i++) {
			if(a%i==0&&b%i==0) {
				list.add(i);
			}
		}
		Collections.reverse(list);
		System.out.println(list.get(k-1));
	}
}

