#!/bin/python3

import math

import os

import random

import re

import sys

from itertools import zip_longest

#

# Complete the 'minimumSwaps' function below.

#

# The function is expected to return an INTEGER.

# The function accepts STRING status as parameter.

#

# NOTE: This only passes the first three test cases.

def minimumSwaps(status):

return min(num_swaps_to_start_with_sale(status), num_swaps_to_start_with_regular(status))

def num_swaps_to_start_with_sale(status):

swaps = 0

groups = grouper(status, 2)

for group in groups:

a, b = group

if(a != None and a != 'S'):

swaps += 1

elif(b != None and b != 'R'):

swaps += 1

return swaps

def num_swaps_to_start_with_regular(status):

swaps = 0

groups = grouper(status, 2)

for group in groups:

a, b = group

if(a != None and a != 'R'):

swaps += 1

elif(b != None and b != 'S'):

swaps += 1

return swaps

def grouper(iterable, n, fillvalue=None):

args = [iter(iterable)] * n

return zip_longest(*args, fillvalue=fillvalue)

if __name__ == '__main__':

fptr = open(os.environ['OUTPUT_PATH'], 'w')

status = input()

result = minimumSwaps(status)

fptr.write(str(result) + '\n')

fptr.close()