'use strict';

const inputs = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n');

const k = parseInt(inputs[0], 10);
const ab = inputs[1].split(' ').map(v => parseInt(v, 10));

if (k === 1) {
  console.log('OK');
  return;
}

if (k === ab[0]) {
  console.log('OK');
  return;
}

let c = Math.floor(ab[0] / k);
if (c === 0) {
  c = 1
}

for (;;) {
  if (c * k < ab[0]) {
    ++c;

    continue;
  }

  if (c * k > ab[1]) {
    break;
  }

  if (c * k % k === 0) {
    console.log('OK');
    return;
  }

  ++c;

  if (c * k > ab[1]) {
    break;
  }
}

console.log('NG');