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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	}
}
 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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	}
} 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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	} main {
		Scanner sc=new Scanner(System.in);
		int a=sc.nextInt();
		int b=sc.nextInt();
		int k=sc.nextInt();
		int count=0;
		int ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	} 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 ans=0; ans 0 int []div=new int[15]; div new int[15] 15 for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		} int i=1; int i=1; i 1 i<=a i a i++ i++ i {
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		} {
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		} if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			} a%i==0 && b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 {
				div[count]=i;
				count++;
			} div[count]=i div[count] div count i count++ count ans=div[count-k] ans div[count-k] div count-k count k System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc 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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	}
} 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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	}
} 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 ans=0;
		int []div=new int[15];

		for(int i=1;i<=a;i++){
			if(a%i==0 && b%i==0 ){
				div[count]=i;
				count++;
			}
		}
		ans=div[count-k];


		System.out.println(ans);
		sc.close();
	}
}

