#include <bits/stdc++.h>
#define For(i, a, b) for(long long i = a; i < b; i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(long long i = a; i >= b; i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

int main() {
    int q;
    lint y;
    cin >> q >> y;
    vector<string> s(q);
    rep(i, q) {
        cin >> s[i];
    }
    auto f = [&](lint x) {
        vector<lint> a;
        rep(i, q) {
            int sz = a.size();
            if (s[i] == "+") {
                a[sz - 2] = min(LINF, a[sz - 2] + a[sz - 1]);
                a.pop_back();
            } else if (s[i] == "max") {
                a[sz - 2] = max(a[sz - 2], a[sz - 1]);
                a.pop_back();
            } else if (s[i] == "min") {
                a[sz - 2] = min(a[sz - 2], a[sz - 1]);
                a.pop_back();
            } else {
                a.emplace_back(s[i] == "X" ? x : stoll(s[i]));
            }
        }
        return a[0];
    };
    if (f(0LL) == y) {
        cout << 0 << endl;
        return 0;
    }
    lint l = 0, r = LINF;
    while (r - l > 1) {
        lint mid = (l + r) / 2;
        if (f(mid) >= y) {
            r = mid;
        } else {
            l = mid;
        }
    }
    cout << (f(r) == y ? r : -1) << endl;
}