import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        
        int a = Integer.parseInt(sc.next());
        int b = Integer.parseInt(sc.next());
        //String s = sc.next();
        
        int tmp=0;
        if(a<b){
            tmp = b;
            b=a;
            a=tmp;
        }
        //a>bになった
        while(a%b>0){
            tmp=a%b;
            a=b;
            b=tmp;
        }
        
        int k = Integer.parseInt(sc.next());
        tmp=0;
        int i=b+1;
        while(tmp<k){
            i--;
            if(b%i==0) tmp++;
        }
        
        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