Remove sequential repeats from python list

I have a list of tuples. First element is index. I need to delete tuples which has subsequent indexes only leaving first tuple from each sequence:

In:
[
  [0, 100],
  [1, 200],
  [5, 600],
  [6, 300],
  [7, 800],
  [9, 300],
  [11, 100],
  [14, 300],
]

Out:
[
  [0, 100],
  [5, 600],
  [9, 300],
  [11, 100],
  [14, 300],
]

>Solution :

Using a simple loop (and assuming l the input list):

prev = -float('inf')
out = []
for x in l:
    if x[0]>prev+1:
        out.append(x)
    prev=x[0]

output: [[0, 100], [5, 600], [9, 300], [11, 100], [14, 300]]