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 s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

}

/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