import 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	}
} import java.util.*; util.* java 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	}
} 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int k = sc.nextInt();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	} 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 for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		} int i = Math.min(a, b); int i = Math.min(a, b); i Math.min(a, b) Math.min Math a b i >= 1 i 1 --i --i i {
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		} {
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		} if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			} a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 {
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			} --k k if (k == 0) 
				{
					System.out.println(i);
				} k == 0 k 0 {
					System.out.println(i);
				} System.out.println(i) System.out.println System.out System System.out i 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	}
} 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	}
} Main
import 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();
		for (int i = Math.min(a, b); i >= 1; --i)
		{
			if (a % i == 0 && b % i == 0)
			{
				--k;
				if (k == 0) 
				{
					System.out.println(i);
				}
			}
		}
	}
}
