import java.util.Scanner;
public class Main {

    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    }
} Main public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    } main {
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    } 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 int i = 0; i 0 int cnt=0; cnt 0 for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	} i = Math.min(a,b); i = Math.min(a,b) i Math.min(a,b) Math.min Math a b i > 0 i 0 i-- i-- i {
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	} {
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	} if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		} a % i == 0 a % i a i 0 {
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		} if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			} b % i == 0 b % i b i 0 {
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			} cnt++ cnt if(cnt == k){
    					break;
    				} cnt == k cnt k {
    					break;
    				} break; System.out.println(i) System.out.println System.out System System.out i String[] args args public class Main {

    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    }
} public class Main {

    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    }
} Main
import java.util.Scanner;
public class Main {

    public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
    	// 入力
    	int a = sc.nextInt();
    	int b = sc.nextInt();
    	int k = sc.nextInt();
    	int i = 0;
    	int cnt=0;

    	for(i = Math.min(a,b); i > 0; i--){
    		if(a % i == 0){
    			if(b % i == 0){
    				cnt++;
    				if(cnt == k){
    					break;
    				}
    			}
    		}
    	}


    	// 出力
    	System.out.println(i);
    }
}