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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    }
} import java.util.*; util.* java 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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    }
} 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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();
        int arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    } 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 arr[] = new int[101]; arr new int[101] 101 for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        } int i = 1; int i = 1; i 1 i <= 100 i 100 i++ i++ i {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        } {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        } if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            } (a % i == 0) && (b % i == 0) (a % i == 0) a % i a i 0 (b % i == 0) b % i b i 0 {
                arr[i] = i;
            } arr[i] = i arr[i] arr i i int count = 0; count 0 for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        } int i = 100; int i = 100; i 100 i >= 0 i 0 i-- i-- i {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        } {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        } if(arr[i] > 0) {
                count++;
            } arr[i] > 0 arr[i] arr 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; 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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    }
} 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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    }
} Main
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 arr[] = new int[101];
        for(int i = 1; i <= 100; i++) {
            if((a % i == 0) && (b % i == 0)) {
                arr[i] = i;
            }
        }
        int count = 0;
        for(int i = 100; i >= 0; i--) {
            if(arr[i] > 0) {
                count++;
            }
            if(count == k) {
                System.out.println(i);
                break;
            }
        }
    }
}
