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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
    } main {
        Scanner sc = new Scanner(System.in);

        int A = sc.nextInt();
        int B = sc.nextInt();
        int K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 K = sc.nextInt(); K sc.nextInt() sc.nextInt sc int x = 0; x 0 if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        } A<=B A B {
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        } for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } int i=A; int i=A; i A i>0 i 0 i-- i-- i {
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } {
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 {
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                } x += 1 x 1 if(x==K){
                        System.out.println(i);
                    } x==K x K {
                        System.out.println(i);
                    } System.out.println(i) System.out.println System.out System System.out i if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        } A>B A B {
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        } for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } int i=B; int i=B; i B i>0 i 0 i-- i-- i {
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } {
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            } if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 {
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                } x += 1 x 1 if(x==K){
                        System.out.println(i);
                    } x==K x K {
                        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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        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 K = sc.nextInt();
        int x = 0;

        if(A<=B){
            for(int i=A; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
        else if(A>B){
            for( int i=B; i>0; i--){
                if(A%i==0 && B%i==0){
                    x += 1;
                    if(x==K){
                        System.out.println(i);
                    }
                }
            }
        }
    }
}