function arrayChange(a: number[]): number {
  let min = 0;
  for (let k = 0; k < a.length - 1; k++) {
    if (a[k] >= a[k + 1]) {
      const dif = a[k] - a[k + 1] + 1;
      a[k + 1] += dif;
      min += dif;
    }
  }

  return min;
}