import java.util.*;
import java.math.*;

public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    // static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    static long[] fact = new long[100];
        public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int k = sc.nextInt();
        int a = sc.nextInt();
        int b = sc.nextInt();
        for(int i = 1;i < 1000;i++){
            if(a<=k*i&&k*i<=b){
                System.out.println("OK");
                return;
            }
        }
        System.out.println("NG");
    }
    
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz