import java.util.Scanner;

class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int count = 0;
		int small = Math.min(A, B);
		for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		}

		
	}
	
	
}
 import java.util.Scanner; Scanner java.util class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int count = 0;
		int small = Math.min(A, B);
		for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		}

		
	}
	
	
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int count = 0;
		int small = Math.min(A, B);
		for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		}

		
	} main {
		Scanner sc = new Scanner(System.in);			//文字の入力
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int count = 0;
		int small = Math.min(A, B);
		for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		}

		
	} 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 count = 0; count 0 int small = Math.min(A, B); small Math.min(A, B) Math.min Math A B for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		} int i = small; int i = small; i small i >= 1 i 1 i-- i-- i {
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		} {
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		} if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			} 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){
					System.out.println(i);
					return;
				}
			} count++ count if(count == C){
					System.out.println(i);
					return;
				} count == C count C {
					System.out.println(i);
					return;
				} System.out.println(i) System.out.println System.out System System.out i return; String[] args args
import java.util.Scanner;

class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int count = 0;
		int small = Math.min(A, B);
		for(int i = small;i >= 1;i--){
			if(A%i == 0 && B%i == 0){
			count++;
				if(count == C){
					System.out.println(i);
					return;
				}
			}
		}

		
	}
	
	
}

