
import java.io.*;
import java.util.*;

class Main{
    public static void main(String[] args){
        solve();
    }

    public static void solve(){
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int x = (int)Math.min(a, b);
        while(true){
        	if(a%x==0 && b%x==0){
        		k--;
        		if(k<1){
        			break;
        		}
        	}
        	x--;
        }
        System.out.println(x);
    }
}
/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