import java.util.*;
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;

        if(a >= b){
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }else{
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }
        System.out.println(ans);
    }
} import java.util.*; util.* java 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;

        if(a >= b){
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }else{
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    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;

        if(a >= b){
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }else{
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    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;

        if(a >= b){
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }else{
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    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 if(a >= b){
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        }else{
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        } a >= b a b {
            for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        } for(int i = a;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } int i = a; int i = a; i a i > 0 i 0 i-- i-- i {
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } {
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                } a%i == 0 && b%i == 0 a%i == 0 a%i a i 0 b%i == 0 b%i b i 0 {
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                } ans = i ans i cnt++ cnt if(cnt == k)
                    break; cnt == k cnt k break; {
            for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            }
        } for(int i = b;i > 0;i--){
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } int i = b; int i = b; i b i > 0 i 0 i-- i-- i {
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } {
                if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                }
            } if(a%i == 0 && b%i == 0){
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                } a%i == 0 && b%i == 0 a%i == 0 a%i a i 0 b%i == 0 b%i b i 0 {
                    ans = i;
                    cnt++;
                    if(cnt == k)
                    break;
                } ans = i ans i cnt++ cnt if(cnt == k)
                    break; cnt == k cnt k break; System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.*;
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;

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