I

#define _CRT_SECURE_NO_DEPRECATE

#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>

#define ull unsigned long long
#define ll long long

using namespace std;

const int N = 1001;
const ll INF = 1000ll * 1000 * 1000 * 1000 * 1000 * 1000ll;

//ll a[N];
ll d[N];


int main() {
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int n;
	cin >> n;
	string s;
	cin >> s;
	d[0] = 0;
	for (int i = 1; i < n; i++) {
		d[i] = -1;
		if (i - 3 >= 0 && s[i - 3] != 'w') {
			d[i] = max(d[i], d[i - 3]);
		}
		if (i - 1 >= 0 && s[i - 1] != 'w') {
			d[i] = max(d[i], d[i - 1]);
		}
		if (i - 5 >= 0 && s[i - 5] != 'w') {
			d[i] = max(d[i], d[i - 5]);
		}
		if (d[i] != -1) {
			if (s[i] == '"') {
				d[i]++;
			}
		}
	}
	cout << d[n - 1];

	return 0;
}