#include <iostream>
#include <vector>
using Int = long long;
int main() {
	int Q;
	Int Y;
	std::cin >> Q >> Y;
	std::string s[Q];
	for (int i = 0; i < Q; ++i) std::cin >> s[i];
	Int lo = -1, hi = Y;
	while (lo + 1 < hi) {
		Int mid = lo + hi >> 1;
		std::vector<Int> A;
		for (int i = 0; i < Q; ++i) {
			if (s[i] == "+") {
				Int x = A[A.size() - 1] + A[A.size() - 2];
				A.pop_back();
				A.pop_back();
				A.push_back(x);
			} else if (s[i] == "min") {
				Int x = std::min(A[A.size() - 1], A[A.size() - 2]);
				A.pop_back();
				A.pop_back();
				A.push_back(x);
			} else if (s[i] == "max") {
				Int x = std::max(A[A.size() - 1], A[A.size() - 2]);
				A.pop_back();
				A.pop_back();
				A.push_back(x);
			} else {
				Int ss;
				if (s[i] == "X") {
					ss = mid;
				} else {
					ss = stoll(s[i]);
				}
				A.push_back(ss);
			}
		}
		(A[0] < Y ? lo : hi) = mid;
	}
	std::vector<Int> A;
	for (int i = 0; i < Q; ++i) {
		if (s[i] == "+") {
			Int x = A[A.size() - 1] + A[A.size() - 2];
			A.pop_back();
			A.pop_back();
			A.push_back(x);
		} else if (s[i] == "min") {
			Int x = std::min(A[A.size() - 1], A[A.size() - 2]);
			A.pop_back();
			A.pop_back();
			A.push_back(x);
		} else if (s[i] == "max") {
			Int x = std::max(A[A.size() - 1], A[A.size() - 2]);
			A.pop_back();
			A.pop_back();
			A.push_back(x);
		} else {
			Int ss;
			if (s[i] == "X") {
				ss = hi;
			} else {
				ss = stoll(s[i]);
			}
			A.push_back(ss);
		}
	}
	std::cout << (A[0] == Y ? hi : -1) << std::endl;
}