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 q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	}
} 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 q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	}
} 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 q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	} main {

		Scanner sc = new Scanner(System.in);

		int a=sc.nextInt();
		int b=sc.nextInt();
		int k=sc.nextInt();
		int q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

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

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	}
} 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 q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	}
} 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 q=0;
		int count=0;
		int answer=0;
		if(b>a){
			q=a;
			a=b;
			b=q;
		}

		for(int i=b;i>0;i--){
			if(a%i==0 && b%i==0){
				count++;
				if(count==k){
					answer=i;
					break;
				}
			}
		}

		System.out.println(answer);

	}
}
