import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int K = sc.nextInt(); K sc.nextInt() sc.nextInt sc int A = sc.nextInt(); A sc.nextInt() sc.nextInt sc int B = sc.nextInt(); B sc.nextInt() sc.nextInt sc int i = 0; i 0 int j = 0; j 0 boolean flg = true; flg true while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        } true {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        } j = K * i j K * i K i i++ i if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            } B < j B j {
                flg = false;
                break;
            } flg = false flg false break; if ( A <= j && j <= B ) {
                break;
            } A <= j && j <= B A <= j A j j <= B j B {
                break;
            } break; if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        } flg {
            System.out.println("OK");
        } System.out.println("OK") System.out.println System.out System System.out "OK" {
            System.out.println("NG");
        } System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        
        int i = 0;
        int j = 0;
        boolean flg = true;
        
        while (true) {
            j = K * i;
            i++;
            if ( B < j ) {
                flg = false;
                break;
            } else if ( A <= j && j <= B ) {
                break;
            }
        }
        
        if (flg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
        
    }
}
