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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    }
} 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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    }
} 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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    } 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 ArrayList<Integer> ans = new ArrayList<>(); ans new ArrayList<>() for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        } int i=1; int i=1; i 1 i<=a i a i++ i++ i {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        } {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        } if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            } a % i == 0 a % i a i 0 {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            } for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                } int j=1; int j=1; j 1 j<=b j b j++ j++ j {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                } {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                } if(b % j == 0 && i == j) {
                        ans.add(i);
                    } b % j == 0 && i == j b % j == 0 b % j b j 0 i == j i j {
                        ans.add(i);
                    } ans.add(i) ans.add ans i Collections.sort(ans, Collections.reverseOrder()) Collections.sort Collections ans Collections.reverseOrder() Collections.reverseOrder Collections System.out.println(ans.get(k-1)) System.out.println System.out System System.out ans.get(k-1) ans.get ans k-1 k 1 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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    }
} 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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    }
} 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();

        ArrayList<Integer> ans = new ArrayList<>();
        for(int i=1; i<=a; i++) {
            if(a % i == 0) {
                for(int j=1; j<=b; j++) {
                    if(b % j == 0 && i == j) {
                        ans.add(i);
                    }
                }
            }
        }

        Collections.sort(ans, Collections.reverseOrder());
        System.out.println(ans.get(k-1));
    }
}
