"use strict";

const main = (input) => {
    const spi = input.split('\n');
    const k = Number(spi[0]);
    const [a, b] = spi[1].split(' ').map(e => Number(e));

    for (let i = a; i <= b; i++) {
        if (i % k == 0) {
            console.log("OK");
            return;
        }
    }

    console.log("NG");
};

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