#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = (int)1e9 + 1001010;
const ll llINF = (long long)4e18 + 22000020;
const string endn = "\n";
template <class T> inline auto vector2(size_t i, size_t j, const T &init = T()) {
    return vector(i, vector<T>(j, init));
}
const string ELM_SEP = " ", VEC_SEP = endn;
template <class T> istream &operator>>(istream &i, vector<T> &A) {
    for(auto &I : A) { i >> I; }
    return i;
}
template <class T> ostream &operator<<(ostream &o, const vector<T> &A) {
    int i = A.size();
    for(const auto &I : A) { o << I << (--i ? ELM_SEP : ""); }
    return o;
}
template <class T> ostream &operator<<(ostream &o, const vector<vector<T>> &A) {
    int i = A.size();
    for(const auto &I : A) { o << I << (--i ? VEC_SEP : ""); }
    return o;
}
template <class T> vector<T> &operator++(vector<T> &A, int) {
    for(auto &I : A) { I++; }
    return A;
}
template <class T> vector<T> &operator--(vector<T> &A, int) {
    for(auto &I : A) { I--; }
    return A;
}
template <class T, class U> bool chmax(T &a, const U &b) { return ((a < b) ? (a = b, true) : false); }
template <class T, class U> bool chmin(T &a, const U &b) { return ((a > b) ? (a = b, true) : false); }
ll floor(ll a, ll b) {
    if(b < 0) a = -a, b = -b;
    return (a >= 0) ? a / b : (a + 1) / b - 1;
}
ll ceil(ll a, ll b) {
    if(b < 0) a = -a, b = -b;
    return (a > 0) ? (a - 1) / b + 1 : a / b;
}
ll bit(unsigned long long val, unsigned long long digit) { return (val >> digit) & 1; }
#ifdef DEBUG
#include <cpp-dump/dump.hpp>
#define dump(...) cpp_dump(__VA_ARGS__)
namespace cp = cpp_dump;
struct InitCppDump {
    InitCppDump() {
        if(!isatty(fileno(stderr))) CPP_DUMP_SET_OPTION(es_style, cpp_dump::es_style_t::no_es);
        CPP_DUMP_SET_OPTION(log_label_func, cp::log_label::line());
        CPP_DUMP_SET_OPTION(max_iteration_count, 30);
    }
} init_cpp_dump;
#else
#define dump(...)
#endif
// ==================== ここまでテンプレ ====================

template<class Judgement>
ll binary_search_ll(ll ok, ll ng, Judgement judge){
    auto need_continue = [&]() -> bool {
        if(ok > ng) return((__int128_t)ok - (__int128_t)ng > 1);
        else return ((__int128_t)ng - (__int128_t)ok > 1);
    };
    while(need_continue()){
        ll mid = ((__int128_t)ok + (__int128_t)ng) / 2;
        if(judge(mid)) ok = mid;
        else ng = mid;
    }
    return ok;
};

int main(int argc, char *argv[]){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll q, y; cin >> q >> y;
    vector<string> s(q); cin >> s;

    auto eval = [&](ll x_val) -> ll {
        vector<ll> a;
        auto parse_int = [&](string s) -> ll {
            if(s == "X") return x_val;
            else return stoll(s);
        };

        for(int i = 0; i < q; i++){
            if(s[i] == "+"){
                ll v1 = a.back(); a.pop_back();
                ll v2 = a.back(); a.pop_back();
                a.push_back(v1 + v2);
            }
            else if(s[i] == "max"){
                ll v1 = a.back(); a.pop_back();
                ll v2 = a.back(); a.pop_back();
                a.push_back(max(v1, v2));
            }
            else if(s[i] == "min"){
                ll v1 = a.back(); a.pop_back();
                ll v2 = a.back(); a.pop_back();
                a.push_back(min(v1, v2));
            }
            else{
                a.push_back(parse_int(s[i]));
            }
        }

        assert(a.size() == 1);
        return a[0];
    };

    auto judge = [&](ll x_val) -> bool {
        dump(x_val);
        dump(eval(x_val));
        return eval(x_val) >= y;
    };

    ll ans = binary_search_ll(1e14, -1, judge);
    dump(ans);

    if(eval(ans) == y) cout << ans << endn;
    else cout << -1 << endn;
    return 0;
}