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

	}

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

	}

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

	} main {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		
		int count = 0;
		int p = Math.max(a, b);
		for(int i = Math.min(a, b); i > 0; i--) {
			if(a % i == 0 && b % i == 0) {
				count++;
			    p = Math.min(i, p);
			}
			if(count == k)
				break;
		}
		
		System.out.println(p);

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

	}

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

	}

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

	}

}
