S = input()

w = 'ｗ'
while S and S[0] == w:
    S = S[1:]

max_wcnt = 0
cands = []
p = 0
while (q := S.find(w, p)) != -1:
    i = q
    while i < len(S) and S[i] == w:
        i += 1

    if i-q > max_wcnt:
        max_wcnt = i-q
        cands.clear()
    if i-q == max_wcnt:
        cands.append(q)

    p = i

for i in cands:
    p = i-1
    res = []
    while p >= 0 and S[p] != w:
        res.append(S[p])
        p -= 1

    print(''.join(reversed(res)))