#include<bits/stdc++.h>
using namespace std;
int n,ans=0;
string s;
int main(){
    freopen("photoshoot_bronze_22open.in","r",stdin);
    freopen("photoshoot_bronze_22open.out","w",stdout);
    cin>>n;
    cin>>s;
    bool k=0;
    int cnt=0;
    for(int i=1;i<=n;i+=2){
        int a=i-1,b=i;
        if(s[a]=='G'&&s[b]=='G')continue;
        if(s[a]=='G'){
            k=1;
        }
        if(s[b]=='G'){
            if(k==1){
                k=0;
                ans++;
                cnt++;
                if(cnt!=1)ans++;
            }
        }
    }
    if(k==1&&cnt==0)ans++;
    if(k==1&&cnt!=0)ans+=2;
    cout<<ans<<endl;
    return 0;
}