#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>

using vii = std::vector<std::pair<int, int> >;
using vi = std::vector<int>;

int resolver(vi& g, vii const& v, int horafin, int i) {
	if (g[i] != -1) return g[i];
	if (i == v.size() - 1) {
		if (v[i].first >= horafin) return g[i] =  1;
		else return g[i] = 0;
	}
	if (v[i].first >= horafin) {
		int a = 1 + resolver(g, v, v[i].first + v[i].second + 10, i + 1);
		int b = resolver(g, v, horafin, i + 1);
		return g[i] = std::max(a, b);
	}
	else return g[i] = resolver(g, v, horafin, i + 1);
}

bool resuelveCaso() {
	int n; std::cin >> n;
	if (n == 0) return false;

	vii peliculas(n);
	for (int i = 0; i < n; ++i) {
		int h, m, t; char aux;
		std::cin >> h >> aux >> m >> t;
		peliculas[i] = std::make_pair(h * 60 + m, t);
	}

	std::sort(peliculas.begin(), peliculas.end());
	vi g(n, -1);

	int sol = resolver(g, peliculas, 0, 0);

	std::cout << sol << std::endl;

	return true;
}

int main() {

	while (resuelveCaso());

	return 0;
}