function solve () {
  let input = document.getElementById('input')
  let output = document.getElementById('output')

  let sentences = input.textContent
    .split('.')
    .filter(x => x !== '')
    .map(x => (x += '.'))

  for (let i = 0; i < sentences.length; i += 3) {
    let p = document.createElement('p')
    p.textContent = sentences.slice(i, i + 3).join('')
    output.appendChild(p)
  }
}