import math
import sys


def main(charges):
    ch = 0
    i = 2
    while i < len(charges):
        if charges[i] == charges[i - 1]:
            ch += 1
        i += 2
    if (ch % 2 != 0):
        ch += 1
    return int(ch/2)


if __name__ == '__main__':
    charges = sys.stdin.readline().strip("\n")
    assert  main("+-+-+--+-+") == 1
    assert  main("+--++-") == 1
    assert main("") == 0
    print(main(charges))