'use strict';
const main = arg => {
  const input = arg.trim().split('\n');
  const K = parseInt(input[0], 10);
  const range = input[1].split(' ').map(n => parseInt(n, 10));

  if (Math.ceil(range[0] / K) * K >= range[0] && Math.ceil(range[0] / K) * K <= range[1]) {
    console.log("OK");
  } else {
    console.log("NG");
  }


  // console.log(K, range, Math.ceil(range[0] / K) * K);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));