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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	}
} 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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	}
} 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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	} main {

		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	} 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 int num = 0; num 0 int count = 0; count 0 for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		} int i = Math.min(a, b); int i = Math.min(a, b); i Math.min(a, b) Math.min Math a b i > 0 i 0 i-- i-- i {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		} {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		} if (a % i == 0 && b % i == 0) {
				count++;
			} a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 {
				count++;
			} count++ count if (count == k) {
				num = i;
				break;
			} count == k count k {
				num = i;
				break;
			} num = i num i break; System.out.print(num) System.out.print System.out System System.out num 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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	}
} 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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	}
} 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();
		int num = 0;
		int count = 0;

		for (int i = Math.min(a, b); i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				count++;
			}
			if (count == k) {
				num = i;
				break;
			}
		}

		System.out.print(num);
	}
}