# coding:utf-8

s = input()
w = "ｗ"
while s[0]==w:
    s = s[1:]

count_w = 0
max_w = 0
word = ""
ans = []
for i in range(len(s)):
    if s[i]==w:
        count_w += 1
    else:
        if count_w > max_w:
            max_w = count_w
            ans = []
            ans.append(word)
        elif count_w == max_w and count_w > 0:
            ans.append(word)
        if count_w != 0:
            word = ""
            count_w = 0
        word += s[i]
if count_w > max_w:
    max_w = count_w
    ans = []
    ans.append(word)
elif count_w == max_w:
    ans.append(word)
# print(max_w,ans)
for i in range(len(ans)):
    print(ans[i])