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.
class CodeforcesTask391ASolution:
    def __init__(self):
        self.result = ''
        self.dna = ''

    def read_input(self):
        self.dna = input()

    def process_task(self):
        currc = ''
        count = 0
        inserts = 0
        for c in self.dna:
            if currc != c:
                currc = c
                if count:
                    if not count % 2:
                        inserts += 1
                count = 1
            else:
                count += 1
        self.result = str(inserts)

    def get_result(self):
        return self.result


if __name__ == "__main__":
    Solution = CodeforcesTask391ASolution()
    Solution.read_input()
    Solution.process_task()
    print(Solution.get_result())
