import re


def main():
    text = input()
    l = text.find('c')
    m = text.find('w', l + 1)
    n = text.find('w', m + 1)

    if text.count('c') < 1 or text.count('w') < 2:
        print(-1)
    elif text.count('c') == 1 and text.count('w') == 1:
        print(-1)
    elif l < m < n:
        patcww = re.compile(r'cx*?wx*?w')
        rescww = patcww.search(text)
        print(len(rescww.group()))
    else:
        print(-1)

    

if __name__ == '__main__':
    main()