function solve (arr, num) {
  if (arr.length === 0) {
    throw new Error()
  }
  let [damagePerHit, stopNumber, rounds] = [
    Math.min(...arr),
    Math.max(...arr),
    1
  ]

  let products = arr
    .slice(0, arr.length / num)
    .reduce((acc, el, i) => {
      acc.push(arr.splice(0, num))
      return acc
    }, [])
    .map(x => x.reduce((acc, el) => acc * el, 1))

  let [firstGiant, secondGiant] = [
    products.slice(0, products.length / 2).reduce((acc, el) => acc + el, 0),
    products.slice(products.length / 2).reduce((acc, el) => acc + el, 0)
  ]

  if (damagePerHit !== 0) {
    while (firstGiant > stopNumber && secondGiant > stopNumber) {
      firstGiant -= damagePerHit
      secondGiant -= damagePerHit
      rounds++
    }
  }

  console.log(
    firstGiant === secondGiant
      ? `Its a draw ${firstGiant} - ${secondGiant}`
      : firstGiant > secondGiant
        ? `First Giant defeated Second Giant with result ${firstGiant} - ${secondGiant} in ${rounds} rounds`
        : `Second Giant defeated First Giant with result ${secondGiant} - ${firstGiant} in ${rounds} rounds`
  )
}