#include <bits/stdc++.h>
using namespace std;

// the tuple (type, fit) has to be unique in the input
#define all(x) begin(x), end(x)
#define sz(x) (ll)(x).size()

using ll = long long;
using ld = long double;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	ll n;
	cin >> n;
	ll socks = 0;
	map<string, ll> count;
	for (ll i = 0; i < n; i++) {
		string a, b;
		ll c;
		cin >> a >> b >> c;
		socks += c;
		if (b == "any") c = 1;
		count[a] = max(count[a], c);
	}
	ll res = 1;
	for (auto e : count) res += e.second;
	if (res > socks) {
		cout << "impossible" << endl;
	} else {
		cout << res << endl;
	}
}