import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    }

    static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    }
} import java.util.ArrayList; ArrayList java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set 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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    }

    static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    }
} 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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    } main {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int k = sc.nextInt();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    } 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 Set<Integer> as = divisor(a); as divisor(a) divisor a Set<Integer> bs = divisor(b); bs divisor(b) divisor b List<Integer> bothDivisor = new ArrayList<>(); bothDivisor new ArrayList<>() for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        } int i = 1; int i = 1; i 1 i <= Math.max(a, b) i Math.max(a, b) Math.max Math a b i++ i++ i {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        } {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        } if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            } as.contains(i) && bs.contains(i) as.contains(i) as.contains as i bs.contains(i) bs.contains bs i {
                bothDivisor.add(i);
            } bothDivisor.add(i) bothDivisor.add bothDivisor i System.out.println(bothDivisor.get(bothDivisor.size() - k)) System.out.println System.out System System.out bothDivisor.get(bothDivisor.size() - k) bothDivisor.get bothDivisor bothDivisor.size() - k bothDivisor.size() bothDivisor.size bothDivisor k String[] args args static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    } divisor {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    } Set<Integer> ret = new HashSet<>(); ret new HashSet<>() for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        } int i = 1; int i = 1; i 1 i * i <= n i * i i i n i++ i++ i {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        } {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        } if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            } n % i == 0 n % i n i 0 {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            } ret.add(i) ret.add ret i if (i != n / i)
                    ret.add(n / i); i != n / i i n / i n i ret.add(n / i) ret.add ret n / i n i return ret; ret int n n 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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    }

    static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    }
} 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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    }

    static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    }
} Main
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

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();

        Set<Integer> as = divisor(a);
        Set<Integer> bs = divisor(b);

        List<Integer> bothDivisor = new ArrayList<>();
        for (int i = 1; i <= Math.max(a, b); i++) {
            if (as.contains(i) && bs.contains(i)) {
                bothDivisor.add(i);
            }
        }

        // k番目。ではなく大きい方からk番目
        System.out.println(bothDivisor.get(bothDivisor.size() - k));
    }

    static Set<Integer> divisor(int n) {
        Set<Integer> ret = new HashSet<>();
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                ret.add(i);
                if (i != n / i)
                    ret.add(n / i);
            }
        }
        return ret;
    }
}
