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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    }
  
} 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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    }
  
} 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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    } main {
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		
		int k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    } 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 k = 0; k 0 for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		} 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) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		} {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		} if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			} A%i == 0 && B%i == 0 A%i == 0 A%i A i 0 B%i == 0 B%i B i 0 {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			} k++ k if (k == C) {
					System.out.println(i);
				} k == C k C {
					System.out.println(i);
				} System.out.println(i) System.out.println System.out System System.out i 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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    }
  
} 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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    }
  
} 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 k = 0;
		for (int i = Math.min(A, B); i > 0; i--) {
			if (A%i == 0 && B%i == 0) {
				k++;
				if (k == C) {
					System.out.println(i);
				}
			}
		}
    }
  
}
