file = open('18.txt')
s = file.readline()
l = 0
kd = 0
ans = 0
for r in range(1, len(s)):
    if s[r] == 'D':
        kd += 1
    while kd >= 2:
        if s[l] == 'D':
            kd -= 1
        l += 1
        ans = max(ans, r - l + 1)
print(ans)