import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    } main {
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc int k = sc.nextInt(); k sc.nextInt() sc.nextInt sc for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        } int i=a<b?a:b; int i=a<b?a:b; i a<b?a:b a<b a b a b i>0 i 0 i-- i-- i {
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        } {
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        } if(a%i==0 && b%i==0) k--; a%i==0 && b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 k-- k if(k==0){
             System.out.println(i);
             return;
          } k==0 k 0 {
             System.out.println(i);
             return;
          } System.out.println(i) System.out.println System.out System System.out i return; String[] args args public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    }
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    }
} Main
import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        for(int i=a<b?a:b;i>0;i--){
          if(a%i==0 && b%i==0) k--;
          if(k==0){
             System.out.println(i);
             return;
          }
        }
        // 出力
       
    }
}
