function main(arg) {
  const inputs = arg.split("\n");
  const k = inputs[0];
  const [a, b] = inputs[1].split(" ");
  
  let isOkay = false;
  
  if (a % k == 0 || (a/k + 1) * k <= b) {
    console.log("OK");
  } else {
    console.log("NG");
  }
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));