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 count = 0;
    int s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

} 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 count = 0;
    int s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

} 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 s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

    for (int i = s; i > 0; i--) {
      if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      }
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int k = sc.nextInt();
    int count = 0;
    int s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

    for (int i = s; i > 0; i--) {
      if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      }
    }
  } 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 s = 0; s 0 if (a > b) {
      s = b;
    } else {
      s = a;
    } a > b a b {
      s = b;
    } s = b s b {
      s = a;
    } s = a s a for (int i = s; i > 0; i--) {
      if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      }
    } int i = s; int i = s; i s i > 0 i 0 i-- i-- i {
      if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      }
    } {
      if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      }
    } if (a % i == 0 && b % i == 0) {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      } a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 {
        count++;
        if (count == k) {
          System.out.println(i);
        }
      } count++ count if (count == k) {
          System.out.println(i);
        } count == k count k {
          System.out.println(i);
        } System.out.println(i) System.out.println System.out System System.out i 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 s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

} 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 s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

} 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 count = 0;
    int s = 0;

    if (a > b) {
      s = b;
    } else {
      s = a;
    }

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

}
