import java.util.Scanner;

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 c = Math.min(a, b);
		int cnt = 0;
		int ans = 0;
		for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		}
		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();
		int b = sc.nextInt();
		int k = sc.nextInt();

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

		int c = Math.min(a, b);
		int cnt = 0;
		int ans = 0;
		for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		}
		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 c = Math.min(a, b); c Math.min(a, b) Math.min Math a b int cnt = 0; cnt 0 int ans = 0; ans 0 for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		} int i = c; int i = c; i c i > 0 i 0 i-- i-- i {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		} {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		} if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			} 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;
					break;
				}
			} cnt++ cnt if (cnt == k) {
					ans = i;
					break;
				} cnt == k cnt k {
					ans = i;
					break;
				} ans = i ans i break; {
				continue;
			} continue; 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 c = Math.min(a, b);
		int cnt = 0;
		int ans = 0;
		for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		}
		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 c = Math.min(a, b);
		int cnt = 0;
		int ans = 0;
		for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		}
		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();
		int b = sc.nextInt();
		int k = sc.nextInt();

		int c = Math.min(a, b);
		int cnt = 0;
		int ans = 0;
		for (int i = c; i > 0; i--) {
			if (a % i == 0 && b % i == 0) {
				cnt++;
				if (cnt == k) {
					ans = i;
					break;
				}
			} else {
				continue;
			}
		}
		System.out.println(ans);
	}

}