import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		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 b=sc.nextInt() b sc.nextInt() sc.nextInt sc k=sc.nextInt(); k sc.nextInt() sc.nextInt sc int min = Math.min(a, b); min Math.min(a, b) Math.min Math a b int cnt=0; cnt 0 int ans=0; ans 0 for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		} int i=min; int i=min; i min 1<=i 1 i i-- i-- i {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		} {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		} if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			} a%i==0 && b%i==0 a%i==0 a%i a i 0 b%i==0 b%i b i 0 {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			} cnt++ cnt if(cnt==k) {
					ans=i;
				} cnt==k cnt k {
					ans=i;
				} ans=i ans i 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(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a=sc.nextInt(),b=sc.nextInt(),k=sc.nextInt();
		int min = Math.min(a, b);
		int cnt=0;
		int ans=0;

		for(int i=min;1<=i;i--) {

			if(a%i==0 && b%i==0) {
				cnt++;
				if(cnt==k) {
					ans=i;
				}
			}

		}
		System.out.println(ans);
	}
}