import java.util.*;

public class Main {
  public static void main(String[] args ) throws Exception {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt();
    int C = sc.nextInt();
    int max_num = Math.max(A,B);
    ArrayList<Integer> num = new ArrayList<Integer>();
    
    for(int i=1;i<=max_num;i++){
     if(B%i==0&&A%i==0){
      num.add(i);
     }
    }
    
    int size=num.size();
    System.out.println(num.get(size-C));
  }
}
/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