import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.stream.*;
import java.util.concurrent.*;
import java.util.regex.*;
import java.util.function.*;
import static java.lang.System.out;

public final class Main {
    public static void main(String[] args) throws Exception {
        try (var input = new Reader()) {
            int k = input.nextInt();
            int a = input.nextInt();
          	int b = input.nextInt();
          	for (int i = a; i <= b; ++i) {
              	if (i % k == 0) {
                  out.printf("OK%n");
                  return;
                }
            }
          	out.printf("NG%n");
        }
    }

    private static final class Reader implements AutoCloseable {
        private final int BUFFER_SIZE = 1 << 16;
        private DataInputStream din;
        private FileInputStream fis;
        private byte[] buffer;
        private int bufferPointer, bytesRead;

        private Reader() {
            din = new DataInputStream(System.in);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        private Reader(String filename) throws IOException {
            fis = new FileInputStream(filename);
            din = new DataInputStream(fis);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        private String readLine() throws IOException {
            byte[] buf = new byte[64]; // line length
            int cnt = 0, c;
            while ((c = read()) != -1) {
                if (c == '\n') { break; }
                buf[cnt++] = (byte) c;
            }
            return new String(buf, 0, cnt);
        }

        private int nextInt() throws IOException {
            int ret = 0;
            byte c = read();
            while (c <= ' ') { c = read(); }
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');

            if (neg) { return -ret; }
            return ret;
        }

        private long nextLong() throws IOException {
            long ret = 0;
            byte c = read();
            while (c <= ' ') { c = read(); }
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');
            if (neg) { return -ret; }
            return ret;
        }

        private double nextDouble() throws IOException {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ') { c = read(); }
            boolean neg = (c == '-');
            if (neg) { c = read(); }
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');

            if (c == '.') {
                while ((c = read()) >= '0' && c <= '9') {
                    ret += (c - '0') / (div *= 10);
                }
            }

            if (neg) { return -ret; }
            return ret;
        }

        private void fillBuffer() throws IOException {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1) { buffer[0] = -1; }
        }

        private byte read() throws IOException {
            if (bufferPointer == bytesRead) { fillBuffer(); }
            return buffer[bufferPointer++];
        }

        @Override
        public void close() throws Exception {
            if (fis != null) {
                fis.close();
            }

            if (din != null) {
                din.close();
            }
        }
    }
}



Measured memory_bytes: 34192