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();
    }
    }
/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