#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int q;
  ll y;
  cin >> q >> y;
  VL ops(q);
  rep(i, q) {
    string s;
    cin >> s;
    if (s == "X") ops[i] = -1;
    else if (s == "+") ops[i] = -2;
    else if (s == "min") ops[i] = -3;
    else if (s == "max") ops[i] = -4;
    else ops[i] = stoll(s);
  }
  constexpr long long INF = 1002003004005006007;
  auto check = [&](ll x) {
    static VL a;
    a.clear();
    for (ll op : ops) {
      if (op == -1) a.emplace_back(x);
      else if (op >= 0) a.emplace_back(op);
      else {
        ll v1 = a.back(); a.pop_back();
        ll v2 = a.back(); a.pop_back();
        if (op == -2) a.emplace_back(min(INF, v1 + v2));
        else if (op == -3) a.emplace_back(min(v1, v2));
        else a.emplace_back(max(v1, v2));
      }
    }
    assert(ssize(a) == 1);
    ll v = a[0];
    return v < y ? -1 : v == y ? 0 : 1;
  };
  ll l = -1, r = y + 1;
  while (r - l > 1) {
    ll c = (l + r) / 2;
    (check(c) >= 0 ? r : l) = c;
  }
  if (check(r) == 0) {
    cout << r << '\n';
  } else {
    cout << -1 << '\n';
  }
}