#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;

template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const dynamic_modint<m>& a) {os << a.val(); return os;}
template <int m> istream& operator>>(istream& is, static_modint<m>& a) {long long x; is >> x; a = x; return is;}
template <int m> istream& operator>>(istream& is, dynamic_modint<m>& a) {long long x; is >> x; a = x; return is;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}
template<typename T> ostream& operator<<(ostream& os, const set<T>& se){for(T x : se) os << x << " "; os << "\n"; return os;}
template<typename T> ostream& operator<<(ostream& os, const unordered_set<T>& se){for(T x : se) os << x << " "; os << "\n"; return os;}
template<typename S, auto op, auto e> ostream& operator<<(ostream& os, const atcoder::segtree<S, op, e>& seg){int n = seg.max_right(0, [](S){return true;}); rep(i, n) os << seg.get(i) << (i == n - 1 ? "\n" : " "); return os;}
template<typename S, auto op, auto e, typename F, auto mapping, auto composition, auto id> ostream& operator<<(ostream& os, const atcoder::lazy_segtree<S, op, e, F, mapping, composition, id>& seg){int n = seg.max_right(0, [](S){return true;}); rep(i, n) os << seg.get(i) << (i == n - 1 ? "\n" : " "); return os;}

template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}

const long long INF = 100100100100100;


int main(){
	int n;
	long long y;
	cin >> n >> y;
	vector<string> t(n);
	cin >> t;
	auto calc = [&](long long x){
		deque<long long> de;
		rep(i, n){
			string s = t[i];
			if(s == "X") de.push_back(x);
			else if(s == "+"){
				auto val1 = de.back(); de.pop_back();
				auto val2 = de.back(); de.pop_back();
				de.push_back(val1 + val2);
			}else if(s == "max"){
				auto val1 = de.back(); de.pop_back();
				auto val2 = de.back(); de.pop_back();
				de.push_back(max(val1, val2));
			}else if(s == "min"){
				auto val1 = de.back(); de.pop_back();
				auto val2 = de.back(); de.pop_back();
				de.push_back(min(val1, val2));
			}else{
				flush(cout);
				long long val = stoll(s);
				flush(cout);
				de.push_back(val);
			}
		}
		long long val = de.back();
		return val;
	};
	long long ng = -1, ok = INF;
	while(ok - ng > 1){
		long long mid = (ok + ng) / 2;
		auto res = calc(mid);
		if(res >= y) ok = mid;
		else ng = mid;
	}
	{
		auto res = calc(ok);
		if(res == y) cout << ok << "\n";
		else cout << "-1\n";
	}
	return 0;
}