
function Main(S) {
  const K = parseInt(S.split("\n")[0]);
  const A = parseInt(S.split("\n")[1].split(" ")[0]);
  const B = parseInt(S.split("\n")[1].split(" ")[1]);
  let ans = '';
  for (let i = A; i <= B; i++) {
      if (i % K === 0) {
          ans = 'OK'
      }
  }

  console.log(ans === '' ? 'NG' : 'OK');
}

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