#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[1000010];
signed main(){
	//freopen("xxx.in","r",stdin);
	//freopen("xxx.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	string s;
	int maxn=0;
	map<int,int> mp;
	cin>>s;
	for(int i=0;i<(int)s.size();i++){
		if(s[i]=='G'){
			a[i+1]=1;
		}else{
			a[i+1]=-1;
		}
		a[i+1]+=a[i];
	}
	int n=(int)s.size(); 
	for(int i=1;i<=n;i++){
		if(a[i]==0){
			maxn=i;
		}
		if(a[i]!=0){
			if(mp[a[i]]!=0){
				maxn=max(maxn,i-mp[a[i]]);
			}else{
				mp[a[i]]=i;
			}
		}
	}
	cout<<maxn;
	return 0;
}