import java.util.*;
public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    }
    public static void main(String[] args) {
        new Main().solve();
    }
    } import java.util.*; util.* java public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    }
    public static void main(String[] args) {
        new Main().solve();
    }
    } Main public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    } solve {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    } 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 for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        } int i=0; int i=0; i 0 i<=B/K i B/K B K i++ i++ i {int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        } {int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        } int C = K*i; C K*i K i if(A<=C && C<=B)
            {System.out.println("OK");return;} A<=C && C<=B A<=C A C C<=B C B {System.out.println("OK");return;} System.out.println("OK") System.out.println System.out System System.out "OK" return; System.out.println("NG") System.out.println System.out System System.out "NG" public static void main(String[] args) {
        new Main().solve();
    } main {
        new Main().solve();
    } new Main().solve() new Main().solve new Main() String[] args args public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    }
    public static void main(String[] args) {
        new Main().solve();
    }
    } public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    }
    public static void main(String[] args) {
        new Main().solve();
    }
    } Main
import java.util.*;
public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        for(int i=0;i<=B/K;i++){int C = K*i;
            if(A<=C && C<=B)
            {System.out.println("OK");return;}
        }System.out.println("NG");
    }
    public static void main(String[] args) {
        new Main().solve();
    }
    }