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

template<class T> istream& operator >> (istream& is, vector<T>& vec) {
    for(T& x : vec) is >> x;
    return is;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll Q, Y;
    cin >> Q >> Y;
    vector<string> a(Q);
    cin >> a;
    auto f = [&](ll x){
        vector<ll> b;
        for(auto &&str : a){
            if(str == "X"){
                b.emplace_back(x);
            }else if('0' <= str[0] && str[0] <= '9'){
                b.emplace_back(stoll(str));
            }else{
                if(str == "+"){
                    b.rbegin()[1] += b.back();
                }else if(str == "max"){
                    b.rbegin()[1] = max(b.rbegin()[1], b.back());
                }else if(str == "min"){
                    b.rbegin()[1] = min(b.rbegin()[1], b.back());
                }
                b.pop_back();
            }
        }
        return b[0];
    };
    ll ng = -1, ok = 100'000'000'000'005ll;
    while(ng + 1 < ok){
        ll mid = (ok + ng) / 2;
        (f(mid) >= Y ? ok : ng) = mid;
    }
    if(f(ok) == Y){
        cout << ok << '\n';
    }else{
        cout << -1 << '\n';
    }
}