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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    System.out.println(ans);
  } main {
    Scanner sc = new Scanner(System.in);

    int a = sc.nextInt();
    int b = sc.nextInt();
    int k = sc.nextInt();
    int buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    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 buf = 0; buf 0 int ans = 0; ans 0 for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    } int i = Math.min(a, b); int i = Math.min(a, b); i Math.min(a, b) Math.min Math a b i > 0 i 0 i-- i-- i {
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    } {
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    } if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      } a % i == 0 && b % i == 0 a % i == 0 a % i a i 0 b % i == 0 b % i b i 0 {
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      } buf += 1 buf 1 if(buf == k){
          ans = i;
          break;
        } buf == k buf k {
          ans = i;
          break;
        } ans = i ans i break; 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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    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 buf = 0;
    int ans = 0;

    for(int i = Math.min(a, b); i > 0; i--){
      if(a % i == 0 && b % i == 0){
        buf += 1;
        if(buf == k){
          ans = i;
          break;
        }
      }
    }

    System.out.println(ans);
  }
}
