import java.util.Scanner;

public class Main6 {

public static void main(String[] args){

Scanner in = new Scanner(System.in);

while(in.hasNext()){

char[] cs = in.nextLine().toCharArray();

int n = cs.length;

System.out.println(minPaint(cs, 0, n-1));

}

}

static int minPaint(char[] cs ,Integer start,int end){

int left = 0;

int right = 0;

int minLeft = 0;

int minRight = 0;

while(cs[start]=='R'&&start<end){

start++;

}

while(cs[end]=='G'&&end>start){

end--;

}

if(start>=end){

return 0;

}

while(cs[start+left]=='G'){

left++;

}

minLeft = left+minPaint(cs, start+left,end);

while(cs[end-right]=='R'){

right++;

}

minRight = right+minPaint(cs, start, end-right);

return Math.min(minLeft, minRight);

}

}