import java.util.Scanner;

class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt(), B = sc.nextInt(), K = sc.nextInt();
		int ans = 0;
		for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		}
		System.out.println(ans);
	}
} import java.util.Scanner; Scanner java.util class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt(), B = sc.nextInt(), K = sc.nextInt();
		int ans = 0;
		for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		}
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt(), B = sc.nextInt(), K = sc.nextInt();
		int ans = 0;
		for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt(), B = sc.nextInt(), K = sc.nextInt();
		int ans = 0;
		for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int A = sc.nextInt() A sc.nextInt() sc.nextInt sc B = sc.nextInt() B sc.nextInt() sc.nextInt sc K = sc.nextInt(); K sc.nextInt() sc.nextInt sc int ans = 0; ans 0 for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		} 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) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		} {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		} if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			} 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) {
					ans = i;
					break;
				}
			} K-- K if(K == 0) {
					ans = i;
					break;
				} K == 0 K 0 {
					ans = i;
					break;
				} ans = i ans i break; System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.Scanner;

class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt(), B = sc.nextInt(), K = sc.nextInt();
		int ans = 0;
		for(int i = Math.min(A, B); i >= 0; i--) {
			if(A % i == 0 && B % i == 0) {
				K--;
				if(K == 0) {
					ans = i;
					break;
				}
			}
		}
		System.out.println(ans);
	}
}