function Main(input) {
  input = input.split("\n");

  K = parseInt(input[0]);
  [A, B] = input[1].split(" ").map((str) => parseInt(str, 10));

  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"));
