const add = (a, b) => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (a < 0 || b < 0) {
        return reject('Numbers must be non-negative')
      }

      resolve(a + b)
    }, 2000)
  })
}

const doWork = async () => {
  const sum = await add(1, -99)
  const sum2 = await add(sum, 50)
  const sum3 = await add(sum2, -3)
  return sum3
}

doWork().then((result) => {
  console.log('result', result)
}).catch((e) => {
  console.log('e', e)
})