#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
using mint = modint998244353;
const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
template <class T, class F>
T binarySearch(T ok, T ng, const F &f) {
	while (abs(ok - ng) > 1) {
		T mid = (ok + ng) / 2;
		(f(mid) ? ok : ng) = mid;
	}
	return ok;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int q; cin >> q;
	long long y; cin >> y;
	vector<string>s(q);
	rep(i, q)cin >> s[i];
	auto f = [&](const long long x)->long long {
		stack<long long>stk;
		rep(i, s.size()) {
			if (s[i] == "+" || s[i] == "min" || s[i] == "max") {
				auto a = stk.top();
				stk.pop();
				auto b = stk.top();
				stk.pop();

				if (s[i] == "+") stk.push(a + b);
				else if (s[i] == "min") stk.push(min(a, b));
				else stk.push(max(a, b));
			}
			else {
				if (s[i] == "X") stk.push(x);
				else stk.push(stoll(s[i]));
			}
		}
		return stk.top();
	};
	auto g = [&](const long long x)->bool {
		return f(x) >= y;
	};
	auto ans = binarySearch<long long>(y + 1, -1, g);
	if (y != f(ans))ans = -1;
	cout << ans << endl;
	return 0;
}