#include<bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 100010;
int n;
string s;
signed main() {
	freopen("photoshoot_bronze_22open.in", "r", stdin);
	freopen("photoshoot_bronze_22open.out", "w", stdout);
	cin >> n >> s;
	int ans = 0, cnt = 0, k = 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;
				cnt ++;
				ans ++;
				if(cnt != 1) {
					ans ++;
				}
			}
		}
	}
	if(k == 1 && cnt == 0) {
		ans ++;
	}
	if(k == 1 && cnt != 0) {
		ans += 2;
	}
	cout << ans;
    return 0;
}