i,j,start,end = 0,0,0,1
  while i<len(intervals_a) and j<len(intervals_b):
    a=intervals_a[i]
    b=intervals_b[j]
    interval = [max(a[start], b[start]), min(a[end], b[end])]
    
    if interval[start]<=interval[end]:
      result.append(interval)
    
    if (a[end] > b[end]):
      j+=1
    else:
      i+=1