const Main = input => {
    const inp = input.split("\n");//["K", "A B"]
    const ab = inp[1].split(" ");//["A", "B"]
    const k = parseInt(inp[0], 10);
    const a = parseInt(ab[0], 10);
    const b = parseInt(ab[1], 10);

    let result = "NG";
    const min = Math.ceil(a / k);
    if(a <= min && min <= b) result = "OK";
    console.log(result);
}

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