function main(input) {
  const inputs = input.trim().split('\n')
  const K = Number(inputs[0])
  const [A, B] = inputs[1].split(' ').map(Number)

  for(let i = A; i <= B; i++) {
    if (i % K === 0) {
      console.log('OK')
      return
    }
  }
  console.log('NG')
}

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