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 c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	}
} 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 c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	} 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 c = sc.nextInt(); c sc.nextInt() sc.nextInt sc int min; min int count = 0; count 0 int result = 0; result 0 if(a < b) min = a;
        else min = b; a < b a b min = a min a min = b min b for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        } int i=min; int i=min; i min i>=1 i 1 i-- i-- i {
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        } {
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        } if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            } 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 == c){
                  result = i;
                  break;
                }
            } count++ count if(count == c){
                  result = i;
                  break;
                } count == c count c {
                  result = i;
                  break;
                } result = i result i break; System.out.println(result) System.out.println System.out System System.out result 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 c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	}
} 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 c = sc.nextInt();
        int min;
        int count = 0;
        int result = 0;
        if(a < b) min = a;
        else min = b;
        for(int i=min; i>=1; i--){
         	if(a % i == 0 && b % i == 0){
             	count++;
                if(count == c){
                  result = i;
                  break;
                }
            }
        }
		System.out.println(result);
	}
}
