
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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	}

} 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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	}

} 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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int K = sc.nextInt();
		int result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	} 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 result = 0; result 0 for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		} int i = Math.min(A,B); int i = Math.min(A,B); i Math.min(A,B) Math.min Math A B K > 0 K 0 i-- i-- i {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		} {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		} if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			} A % i == 0 && B % i == 0 A % i == 0 A % i A i 0 B % i == 0 B % i B i 0 {
				K--;
				result = i;
			} K-- K result = i result i System.out.println(result) System.out.println System.out System System.out result 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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	}

} 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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	}

} 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 result = 0;

		for(int i = Math.min(A,B); K > 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				result = i;
			}
		}
		System.out.println(result);
	}

}
