24 минимальная ровно 3 X

s = open('').readline()
cnt_x = 0
l = 0
r = 0
while cnt_x == 0:
    l += 1
    r += 1
    if s[l] == 'X':
        cnt_x += 1
answ = 1000000000
while r < len(s):
    while r < len(s) and cnt_x != 3:
        r += 1
        if r < len(s) and s[r] == 'X':
            cnt_x += 1
    answ = min(answ, r - l + 1)
    l += 1
    while s[l] != 'X':
         l += 1
    cnt_x -= 1
print(answ)