You will receive 3 points for solving this problem.

Manao is designing the genetic code for a new type of algae to efficiently produce fuel. Specifically, Manao is focusing on a stretch of DNA that encodes one protein. The stretch of DNA is represented by a string containing only the characters 'A', 'T', 'G' and 'C'.

Manao has determined that if the stretch of DNA contains a maximal sequence of consecutive identical nucleotides that is of even length, then the protein will be nonfunctional. For example, consider a protein described by DNA string "GTTAAAG". It contains four maximal sequences of consecutive identical nucleotides: "G", "TT", "AAA", and "G". The protein is nonfunctional because sequence "TT" has even length.

Manao is trying to obtain a functional protein from the protein he currently has. Manao can insert additional nucleotides into the DNA stretch. Each additional nucleotide is a character from the set {'A', 'T', 'G', 'C'}. Manao wants to determine the minimum number of insertions necessary to make the DNA encode a functional protein.
The input consists of a single line, containing a string *s* of length *n* (1 ≤ *n* ≤ 100). Each character of *s* will be from the set {'A', 'T', 'G', 'C'}.

This problem doesn't have subproblems. You will get 3 points for the correct submission.
s = input()
result = 0
last_ch = s[0]
last_ch_len = 1
for i in range(1, len(s)):
    if s[i] == last_ch:
        last_ch_len += 1
    else:
        if last_ch_len%2 == 0:
            result += 1
        last_ch_len = 1
        last_ch = s[i]
    #print('{} {} {} {}'.format(s[i], last_ch, last_ch_len, result))
if last_ch_len%2 == 0:
    result += 1
print(result)
