#include<iostream>
#include<vector>
using namespace std;
int solve(vector<pair<int, int>>x) {
	int minx = 9999, minid = -1;
	for (int i = 0; i < x.size(); i++) {
		if (x[i].second == 0 && minx > x[i].first) { minx = x[i].first; minid = i; }
	}
	if (minx == 9999)return 0;
	int L = minid; while (L >= 1 && (x[L - 1].second == 0 || x[L - 1].first < minx))L--;
	int R = minid; while (R < x.size() - 1 && (x[R + 1].second == 0 || x[R + 1].first < minx))R++;
	vector<pair<int, int>>J;
	for (int i = 0; i < x.size(); i++) { if (L <= i && i <= R)continue; J.push_back(x[i]); }
	return solve(J) + 1;
}
int main() {
	vector<pair<int, int>>r; int n; cin >> n;
	for (int i = 0; i < n; i++) {
		int t1; char c2; cin >> c2 >> t1;
		if (c2 == 'y')r.push_back(make_pair(t1, 0)); else r.push_back(make_pair(t1, 1));
	}
	cout << solve(r) << endl;
	return 0;
}