```
class Solution:
# @param A a list of integers
# @return an integer
def removeDuplicates(self, A):
if A is None:
return 0
length = len(A)
result = 0
i = j = 0
while i < length:
j = i
while j < length:
if A[j] != A[i]:
break
j += 1
if j-i > 2:
length -= j-i-2
for k in range(j-i-2):
del A[i]
result += 2
j = i+2
else:
result += (j-i)
i = j
return result
```