import java.io.BufferedReader;
import java.io.InputStreamReader;


public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    }

    public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    }

    private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    }

    public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    }

    private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    }
} Main public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    } main {
        Main main = new Main();
        main.solve(args);
    } Main main = new Main(); main new Main() main.solve(args) main.solve main args String[] args args public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    } solve {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    } MyScanner scanner = new MyScanner(); scanner new MyScanner() int a = scanner.nextInt(); a scanner.nextInt() scanner.nextInt scanner int b = scanner.nextInt(); b scanner.nextInt() scanner.nextInt scanner int k = scanner.nextInt(); k scanner.nextInt() scanner.nextInt scanner int n = 0; n 0 if(a>b){
        	n=b;
        }else {
        	n=a;
        } a>b a b {
        	n=b;
        } n=b n b {
        	n=a;
        } n=a n a int cnt = 0; cnt 0 for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        } int i=n; int i=n; i n i>0 i 0 i-- i-- i {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        } {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        } if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	} (a%i==0)&&(b%i==0) (a%i==0) a%i a i 0 (b%i==0) b%i b i 0 {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	} cnt++ cnt if(cnt==k) {
        			System.out.println(i);
        			break;
        		} cnt==k cnt k {
        			System.out.println(i);
        			break;
        		} System.out.println(i) System.out.println System.out System System.out i break; String[] args args private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    } MyScanner String[] s; s int i; i BufferedReader br; br String reg = " "; reg " " MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        } MyScanner {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        } s = new String[0] s new String[0] 0 i = 0 i 0 br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        } next {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        } try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} Exception e {e.printStackTrace();} e.printStackTrace() e.printStackTrace e {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } if (i < s.length) return s[i++]; i < s.length i s.length s s.length return s[i++]; s[i++] s i++ i String line = br.readLine(); line br.readLine() br.readLine br while (line.equals("")) {line = br.readLine();} line.equals("") line.equals line "" {line = br.readLine();} line = br.readLine() line br.readLine() br.readLine br s = line.split(reg, 0) s line.split(reg, 0) line.split line reg 0 i = 0 i 0 return s[i++]; s[i++] s i++ i return null; null public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } nextInt {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} Exception e {e.printStackTrace();} e.printStackTrace() e.printStackTrace e {return Integer.parseInt(next());} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next return -1; -1 1 public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } nextDouble {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} Exception e {e.printStackTrace();} e.printStackTrace() e.printStackTrace e {return Double.parseDouble(next());} return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next return -1; -1 1 public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } nextLong {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        } try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} Exception e {e.printStackTrace();} e.printStackTrace() e.printStackTrace e {return Long.parseLong(next());} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next return -1; -1 1 public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    }

    public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    }

    private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    }
} public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    }

    public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    }

    private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    }
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;


public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve(args);
    }

    public void solve(String[] args) {
        MyScanner scanner = new MyScanner();

        // 数取得
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int k = scanner.nextInt();


        // ループの開始
        int n = 0;
        if(a>b){
        	n=b;
        }else {
        	n=a;
        }

        // カウンタ
        int cnt = 0;

        for(int i=n;i>0;i--) {
        	if((a%i==0)&&(b%i==0)) {
        		cnt++;
        		if(cnt==k) {
        			System.out.println(i);
        			break;
        		}
        	}
        }
    }

    private class MyScanner {
        String[] s;
        int i;
        BufferedReader br;
        String reg = " ";
        MyScanner () {
            s = new String[0];
            i = 0;
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public String next() {
            try {
                if (i < s.length) return s[i++];
                String line = br.readLine();
                while (line.equals("")) {line = br.readLine();}
                s = line.split(reg, 0);
                i = 0;return s[i++];
            } catch (Exception e) {e.printStackTrace();}
            return null;
        }
        public int nextInt() {
            try {return Integer.parseInt(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public double nextDouble() {
            try {return Double.parseDouble(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
        public long nextLong()  {
            try {return Long.parseLong(next());} catch (Exception e) {e.printStackTrace();}
            return -1;
        }
    }
}