f = open('24-153.txt')
s = f.readline()
numbersD = []
for i in range(len(s)):
    if s[i] == 'D':
        numbersD += [i]
k = len(numbersD)
for i in range(1, len(numbersD)):
    if numbersD[i] - numbersD[i-1] < k and numbersD[i]- numbersD[i-1] != 1:
        k = numbersD[i] - numbersD[i-1]
print(k+1)