if __name__ == '__main__':
    input = input()
    signs = []
    for char in input:
        signs.append(char)

    result = 0
    mistake = False
    i = 0
    while i < len(signs)-1:
        if signs[i] == signs[i+1]:
            err_sign = signs[i]
            j = i+1
            if j < len(signs):
                while j < len(signs):
                    if signs[j] == signs[j+1] and err_sign != signs[j]:
                        j += 1
                        break
                    j += 1
                    if j == len(signs) - 1:
                        j += 1
                        break
                var = signs[i + 1:j][::-1]
                if signs != var:
                    signs[i+1:j] = var
                    result += 1
        i += 1
    print(result)