import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            new Main().solve(sc);
        }
    }

    void solve(Scanner sc) {
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int count = 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;
            }
        }
    }
}

/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