const Main = (input) => {
  const tmp = input.trim().split('\n')
  const K = parseInt(tmp[0])
  const A = parseInt(tmp[1].split(' ')[0])
  const B = parseInt(tmp[1].split(' ')[1])

  let result = 'NG'

  for (let i = A; i <= B; i++) {
    if ((i % K) === 0) {
      result = 'OK'
    }
  }

  console.log(result)
  return result
}

Main(require('fs').readFileSync('/dev/stdin', 'utf8'))