function Main(input) {
    tmp = input.split("\n");
    k = parseInt(tmp[0], 10);
    tmp2 = tmp[1].split(" ");
    a = parseInt(tmp2[0], 10);
    b = parseInt(tmp2[1], 10);
    result = "NG";

    for (let i = a; i <= b; i++) {
        if (i % k == 0) {
            result = "OK";
        }
    }

    console.log(result);

}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));