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 x[]=new int[B];
		int y=0;
		
		for(int i=1;i<=B;i++) {
			if(A%i==0&&B%i==0) {
				x[y]=i;
				y++;
				
			}
			
		}
		System.out.println(x[y-K]);
}
}
/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