#include <cstdio>
#include <iostream>
#include <sstream>
using namespace std;

typedef long long LL;

int T[1024];
LL year[1024];
bool keep[1024];
int dp[1024][1024];
const int oo = 1000000;

LL toLL(string t)
{
	int n = t.size();
	for (int i=0; i<n; i++)
		if (t[i] == ':')
			t[i] = ' ';
	istringstream is(t);
	LL mo, da, ho, mi;
	is >> mo >> da >> ho >> mi;
	LL ret = mo;
	ret *= 32;
	ret += da;
	ret *= 25;
	ret += ho;
	ret *= 61;
	ret += mi;
	return ret;
}
int main()
{
	freopen("economic.in", "r", stdin);
	int n;
	while (cin >> n, n)
	{
		for (int i=0; i<n; i++)
		{
			string t, tmp, k;
			cin >> t >> tmp >> k;
			T[i] = toLL(t);
			keep[i] = (k == "+");
		}
		year[n-1] = 1023;
		for (int i=n-2; i>=0; i--)
			year[i] = (T[i] < T[i+1] ? year[i+1] : year[i+1]-1);
		for (int i=0; i<1024; i++)
			for (int j=0; j<n; j++)
				dp[j][i] = oo;
		for (int i=n-1; i>=0; i--)
		{
			if (year[i] != 1023)
				break;
			dp[i][1023] = 1;
			if (keep[i])
				break;
		}
		int res = 0;
		for (int i=n-1; i>=0; i--)
		{
			if (keep[i])
			{
				for (int j=i+1; j<n; j++)
				{
					if (T[i] < T[j])
						dp[i][year[i]] <?= dp[j][year[i]] + 1;
					else if (year[i] + 1 < 1024)
						dp[i][year[i]] <?= dp[j][year[i]+1] + 1;
					if (keep[j])
						break;
				}
				res >?= dp[i][year[i]];
			}
			else
			{
				for (int j=i+1; j<n; j++)
				{
					if (T[i] < T[j])
					{
						for (int k=0; k<1024; k++)
							dp[i][k] <?= dp[j][k] + 1;
					}
					else
					{
						for (int k=0; k<1023; k++)
							dp[i][k] <?= dp[j][k+1] + 1;
					}
					if (keep[j])
						break;
				}
			}
		}
		cout << res << endl;
	}
	return 0;
}