file = open('5.txt')
A = file.readline()
l = 0
ka = 0
kd = 0
ans = 0
for r in range(len(A)):
    if A[r] == 'A':
        ka += 1
    if A[r] == 'D':
        kd += 1
    while ka >= 1 or kd >= 1:
        if A[l] == 'A':
            ka -= 1
        if A[l] == 'D':
            kd -= 1
        l += 1
    ans = max(ans, r - l + 1)
print(ans)