const Main = input => {
  const sp = input.split('\n');
  const K = Number(sp[0]);
  const AB = sp[1].split(' ').map(e => Number(e));

  const A_ex = Math.floor(AB[0] / K);
  const A_mod = AB[0] % K;
  const B_ex = Math.floor(AB[1] / K);
  const B_mod = AB[1] % K;

  console.log((A_mod===0 || B_mod===0 || A_ex < B_ex) ? 'OK' : 'NG');
};

Main(require('fs').readFileSync('/dev/stdin', 'utf8').trim());
/*Main(`7
500 600`);
Main(`4
5 7`)
Main(`1
11 11`)*/
