"use strict";

const main = arg => {
    const inputList = arg.trim().split("\n");
    // 回答を記述
    const K = parseInt(inputList[0]);
    const A = parseInt(inputList[1].split(" ")[0])
    const B = parseInt(inputList[1].split(" ")[1])
    if (A % K == 0) {
        console.log("OK");
    } else {
        let i = 0;
        i = (A / K) + 1;
        if (K * i <= B) {
            console.log("OK");
        } else {
            console.log("NG");
        }
    }
}

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