function main(input) {
  let a, b;
  const k = parseInt(input[0]);
  [a, b] = input[1].trim().split(" ").map(i => parseInt(i));

  let judge=false;

  for(let i=a;i<=b;i++){
    if(i%k===0){
      judge =true;
    }
  }
  console.log((judge)?"OK":"NG");
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"));