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