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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	}
} 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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	}
} 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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	} 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 for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		} int i = Math.max(a, b); int i = Math.max(a, b); i Math.max(a, b) Math.max Math a b i > 0 i 0 i-- i-- i {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		} {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		} if(a %i != 0 || b % i != 0)
				continue; a %i != 0 || b % i != 0 a %i != 0 a %i a i 0 b % i != 0 b % i b i 0 continue; if(--k == 0) {
				System.out.println(i);
				return;
			} --k == 0 --k k 0 {
				System.out.println(i);
				return;
			} System.out.println(i) System.out.println System.out System System.out i return; 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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	}
} 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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	}
} Main
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();
		for(int i = Math.max(a, b); i > 0; i--) {
			if(a %i != 0 || b % i != 0)
				continue;
			
			if(--k == 0) {
				System.out.println(i);
				return;
			}
		}
	}
}
