from collections import OrderedDict

str = input()

d = OrderedDict()
s = ""
count = 0

for i in str:
    if i != 'ｗ' and count == 0:
        s += i
    elif i == 'ｗ':
        count += 1
    else:
        if s == "":
            pass
        else:
            d[s] = count
        s = i
        count = 0
else:
    d[s] = count
m = 0

for key, val in d.items():
    m = max(m, val)

if m == 0:
    print()
else:
    for key, val in d.items():
        if val == m:
            print(key)