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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	}
}

//Arrays.sort(array, (a, b) -> Integer.compare(a[0], b[0]));

 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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	}
} 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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		int count=0;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	} 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 for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		} int i=Math.max(a, b); int i=Math.max(a, b); i Math.max(a, b) Math.max Math a b i>=1 i 1 i-- i-- i {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		} {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(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) {
				System.out.println(i);
				break;
			} count==k count k {
				System.out.println(i);
				break;
			} System.out.println(i) System.out.println System.out System System.out i break; 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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	}
} 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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	}
} 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;

		for(int i=Math.max(a, b);i>=1;i--) {
			if(a%i==0&&b%i==0) {
				count++;
			}
			if(count==k) {
				System.out.println(i);
				break;
			}
		}
	}
}

//Arrays.sort(array, (a, b) -> Integer.compare(a[0], b[0]));


