import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner sn = new Scanner(System.in);
        int a = sn.nextInt();
        int b = sn.nextInt();
        int k = sn.nextInt();
        
        List<Integer> commonDiviserList = new ArrayList<>();
        int c = a > b ? b : a;
        for (int i = c; i >= 1; i--){
            if(a % i == 0 && b % i == 0){
                commonDiviserList.add(i);
            }
        }
        
        System.out.println(commonDiviserList.get(k - 1));        
    }
}
/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