import java.util.Scanner;

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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    }
} import java.util.Scanner; Scanner 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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    }
} 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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    } 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 count = 0; count 0 int smaller = a <= b ? a : b; smaller a <= b ? a : b a <= b a b a b for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        } int i=smaller; int i=smaller; i smaller i >= 1 i 1 i-- i-- i {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        } {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        } if (a % i == 0 && b % i == 0) {
                count++;
            } a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 {
                count++;
            } count++ count if (count == k) {
                System.out.println(i);
                break;
            } count == k count k {
                System.out.println(i);
                break;
            } System.out.println(i) System.out.println System.out System System.out i break; sc.close() sc.close sc String[] args args 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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    }
} 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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    }
} Main
import java.util.Scanner;

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 count = 0;
        int smaller = a <= b ? a : b;
        for (int i=smaller; i >= 1; i--) {
            if (a % i == 0 && b % i == 0) {
                count++;
            }
            if (count == k) {
                System.out.println(i);
                break;
            }
        }
        sc.close();
    }
}