
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int A = scan.nextInt();
		int B = scan.nextInt();
		int K = scan.nextInt();
		int min = 0;
		int count = 0;

		if (A < B) {
			min = A;
		} else {
			min = B;
		}

		for (int i = min; i >= 1; i--) {
			if(A%i==0 && B%i==0) {
				count++;
				if(count==K) {
					System.out.println(i);
					break;
				}
			}
		}
		scan.close();
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz