from collections import deque

s = input()
dq = deque()
cww = deque()
mn = float("inf")
for c in s:
    for i in range(len(dq)):
        dq[i] += 1
    if c == "c":
        dq.append(1)
        cww.append(0)
    if c == "w":
        for i in range(len(dq)):
            cww[i] += 1
        while cww and cww[0] == 2:
            cww.popleft()
            mn = min(mn, dq.popleft())
print(mn if mn != float("inf") else -1)