#include <bits/stdc++.h>
using namespace std;
long long n,sum[2000000],maxx=-1,k,ans;
map<long long,long long> mp;
string a='0'+a;
int main(){
   ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>a;
	mp[0]=0;
	for(int i=1;i<a.size();i++){
		if(a[i]=='G'){
			sum[i]=sum[i-1]+1;
		}else{
			sum[i]=sum[i-1]-1;
		}
		if(mp.find(sum[i])==mp.end()){
			mp[sum[i]]=i;
		}else{
			ans=max(ans,i-mp[sum[i]]);
		}
	}
	cout<<ans;
	return 0;
}

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R1JHR1JH

GRGGRG