function Main (input) {
  input = input.split("\n");
  var number = input[1].split(" ");
  var k = parseInt(input[0], 10);
  var a = parseInt(number[0], 10);
  var b = parseInt(number[1], 10);
  
  if (a%k === 0 || (b-a) >= (k-a%k)) {
    console.log("OK");
  } else {
    console.log("NG");
  }
}
 
Main(require("fs").readFileSync("/dev/stdin", "utf8"));