import java.util.Scanner;

public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
} Main public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    } main {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int K = scan.nextInt(); K scan.nextInt() scan.nextInt scan int A = scan.nextInt(); A scan.nextInt() scan.nextInt scan int B = scan.nextInt(); B scan.nextInt() scan.nextInt scan int Kc = K; Kc K while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        } true {
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        } if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            } Kc <= B Kc B {
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            } if(Kc >= A){
                    System.out.println("OK");
                    break;
                } Kc >= A Kc A {
                    System.out.println("OK");
                    break;
                } System.out.println("OK") System.out.println System.out System System.out "OK" break; if(Kc > B){
                System.out.println("NG");
                break;
            } Kc > B Kc B {
                System.out.println("NG");
                break;
            } System.out.println("NG") System.out.println System.out System System.out "NG" break; Kc = Kc + K Kc Kc + K Kc K final String args[] args public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
} public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
} Main
import java.util.Scanner;

public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
}