file = open('6.txt')
A = file.readline()
l = 3
k0 = 0
k1 = 0
k = 0
ans = 0
for r in range(4, len(A)):
    if A[r] in '02468':
        k0 += 1
    if A[r] in '13579':
        k1 += 1
    while k0 >= 1 or k1 >= 1:
        if k0 >= 1 and A[l] in '13579':
            k0 -= 1
            l += 1
        if k1 >= 1 and A[l] in '02468':
            k1 -= 1
            l += 1
        else:
            k0 = 0
            k1 = 0
            l = r
    ans = max(ans, r - l + 1)
print(ans)