#include <iostream>
#include <string>
#include <unordered_map>
#include <vector>

struct SockInfo { int left = 0, right = 0, any = 0; };

int main() {
	int n;
	std::cin >> n;

	std::string name, type;
	int count;
	std::unordered_map<std::string, SockInfo> infos;
	while (std::cin >> name >> type >> count) {
		auto& sockInfo = infos[name];
		if (type[0] == 'l') sockInfo.left += count;
		if (type[0] == 'a') sockInfo.any += count;
		if (type[0] == 'r') sockInfo.right += count;
	}

	int ans = 1;
	bool possible = false;
	for (const auto& [_, sockInfo] : infos) {
		ans += std::max(1, std::max(sockInfo.left, sockInfo.right));
		if ((std::min(1, sockInfo.left) + std::min(1, sockInfo.right) + sockInfo.any) >= 2)
			possible = true;
	}

	if (possible)
		std::cout << ans << std::endl;
	else	std::cout << "impossible" << std::endl;
}