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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  } main {
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int k = sc.nextInt();
    int ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  } 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 ans = 0; ans 0 int p = 1; p 1 for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    } int i = Math.min(a, b); int i = Math.min(a, b); i Math.min(a, b) Math.min Math a b i >= 1 i 1 i-- i-- i {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    } {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    } if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      } ((a % i) == 0) && ((b % i) == 0) ((a % i) == 0) (a % i) a i 0 ((b % i) == 0) (b % i) b i 0 {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      } if(p == k) {
          ans = i;
        } else {
          
        } p == k p k {
          ans = i;
        } ans = i ans i {
          
        } p++ p System.out.println(ans) System.out.println System.out System System.out ans 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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int p = 1;
    for(int i = Math.min(a, b); i >= 1; i--) {
      if(((a % i) == 0) && ((b % i) == 0)) {
        if(p == k) {
          ans = i;
        } else {
          
        }
        p++;
      }
    }
    System.out.println(ans);
  }
}