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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        System.out.println(ans);
	} main {
		 Scanner sc = new Scanner(System.in);
	        int A = sc.nextInt();
	        int B = sc.nextInt();
	        int K = sc.nextInt();
	        int cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        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 cnt = 0; cnt 0 int ans = 0; ans 0 for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        } int i=100; int i=100; i 100 i>0 i 0 i-- i-- i {
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        } {
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        } if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	} A % i == 0 A % i A i 0 {
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	} if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		} B % i == 0 B % i B i 0 {
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		} cnt = cnt +1 cnt cnt +1 cnt 1 if (K == cnt){
	        				ans = i;
	        				break;
	        			} K == cnt K cnt {
	        				ans = i;
	        				break;
	        			} ans = i ans i break; 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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        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 cnt = 0;
	        int ans = 0;
	        
	        for(int i=100; i>0; i--){
	        	if(A % i == 0){
	        		if(B % i == 0){
	        			cnt = cnt +1;
	        			if (K == cnt){
	        				ans = i;
	        				break;
	        			}
	        		}
	        	}
	        }
	        System.out.println(ans);
	}
}