#include <bits/stdc++.h>
using namespace std;
#define rep(E, F) for (E = 0; E < (F); E++)
#define per(E, F) for (E = (F) - 1; E >= 0; E--)
typedef vector<int> vi;

int get_int()
{
	int r = 0, c = getchar(), s = 1;
	while (c != '-' && c < '0' || c > '9') c = getchar();
	while (c == '-') s *= -1, c = getchar();
	while (c >= '0' && c <= '9') r = r*10 + c - '0', c = getchar();
	return s*r;
}

int get_string(char* b, char t)
{
	int i = 0;
	b[i++] = getchar();
	while (b[i - 1] != t) b[i++] = getchar();
	b[i - 1] = '\0';
	return i - 1;
}

int goo(int l, int a, int r)
{
	fprintf(stderr, ">> %d %d %d\n", l, a, r);
	if (l != 0 && r != 0) return 1;
	if (a > 1) return 1;
	if (a == 1 && (l != 0 || r != 0)) return 1;
	return 0;
}

int foo(int l, int a, int r)
{
	if (!goo(l, a, r)) return a + l + r;
	if (a == 0) return max(l, r);
	return max(max(l, r), 1);
}

int main()
{
	int n = get_int(), x, r = 0, b = 0;
	map<string, vi> m;
	char c, s[32];
	while (n--)
	{
		get_string(s, ' ');
		c = getchar();
		x = get_int();
		if (m.find(s) == m.end()) m[s] = vi(3);
		if (c == 'l') m[s][0] += x;
		else if (c == 'a') m[s][1] += x;
		else if (c == 'r') m[s][2] += x;
		else assert(0);
	}
	for (auto it : m) if (goo(it.second[0], it.second[1], it.second[2])) { b = 1; break; }
	if (!b)
	{
		printf("impossible\n");
		return 0;
	}
	for (auto it : m) r += foo(it.second[0], it.second[1], it.second[2]);
	printf("%d\n", r + 1);
	return 0;
}