#include<iostream>
#include<unordered_map>
using namespace std;
struct sock{
	string op;
	int cnt;
};
unordered_map<string,int> m;
int main(){
	int res=0;
	int n;
	cin>>n;
	string type,op;
	int cnt;
	bool flag=false;
	for(int i=0;i<n;++i){
		cin>>type>>op>>cnt;
		if(op=="any"&&cnt>=2) flag=true;
		if(m.find(type)!=m.end()){
			flag=true;
			if(op!="any"&&m[type]<cnt) m[type]=cnt;
		}
		else{
			if(op=="any") m[type]=1;
			else m[type]=cnt; 
		}
	}
	if(flag){
		for(unordered_map<string,int>::iterator it=m.begin();it!=m.end();++it) res+=it->second;
		cout<<res+1; 
	}
	else cout<<"imopssible";
	return 0;
}