function main(input) {
  const lines = input.trim().split("\n");
  const K = +lines[0];
  const [A, B] = lines[1].split(' ').map(Number);

  let res = 'NG';
  let d, i = 1;
  while (d = K * i, d <= B) {
    if (d >= A) {
      res = 'OK';
      break;
    }
    i++;
  }

  console.log(res);
}

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