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

void fast_io() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
}

int main() {
	fast_io();
	int q;
	long long y;
	cin >> q >> y;
	vector<string> s(q);
	for (int i = 0; i < q; i++) {
		cin >> s[i];
	}
	long long ng = -1, ok = y + 1;
	while (ng + 1 < ok) {
		long long x = (ng + ok) / 2;
		vector<long long> st;
		for (int i = 0; i < q; i++) {
			if (s[i] == "+") {
				long long a = st.back();
				st.pop_back();
				long long b = st.back();
				st.pop_back();
				st.push_back(min(y + 1, a + b));
			} else if (s[i] == "min") {
				long long a = st.back();
				st.pop_back();
				long long b = st.back();
				st.pop_back();
				st.push_back(min(a, b));
			} else if (s[i] == "max") {
				long long a = st.back();
				st.pop_back();
				long long b = st.back();
				st.pop_back();
				st.push_back(max(a, b));
			} else if (s[i] == "X") {
				st.push_back(x);
			} else {
				st.push_back(stoll(s[i]));
			}
		}
		if (st[0] < y) {
			ng = x;
		} else {
			ok = x;
		}
	}
	vector<long long> st;
	for (int i = 0; i < q; i++) {
		if (s[i] == "+") {
			long long a = st.back();
			st.pop_back();
			long long b = st.back();
			st.pop_back();
			st.push_back(min(y + 1, a + b));
		} else if (s[i] == "min") {
			long long a = st.back();
			st.pop_back();
			long long b = st.back();
			st.pop_back();
			st.push_back(min(a, b));
		} else if (s[i] == "max") {
			long long a = st.back();
			st.pop_back();
			long long b = st.back();
			st.pop_back();
			st.push_back(max(a, b));
		} else if (s[i] == "X") {
			st.push_back(ok);
		} else {
			st.push_back(stoll(s[i]));
		}
	}
	if (st[0] == y) {
		cout << ok << endl;
	} else {
		cout << -1 << endl;
	}
}