function Main(input) {
    var K = parseInt(input[0], 10)
    var A = parseInt(input[1], 10)
    var B = parseInt(input[2], 10)

    for (var i = A; i <= B; i++) {
        if (i % K === 0) {
            console.log('OK');
            return;
        }
    }
    console.log('NG');
}

Main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split(/\n|\s/));