#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, x, y) for (auto i = (x); i < (y); i++)
#define RREP(i, x, y) for (auto i = (y) - 1; (x) <= i; i--)
#define ALL(x) (x).begin(), (x).end()
#pragma GCC optimize("O3")
int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll Q, Y;
  cin >> Q >> Y;
  vector<string> S(Q);
  REP(i, 0, Q){
    cin >> S[i];
  }
  {
    vector<ll> A;
    REP(i, 0, Q){
      if(S[i] == "X"){
        A.push_back(100000000000005LL);
      }else if(S[i] == "+"){
        ll tmp = A[ssize(A)-1] + A[ssize(A)-2];
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "min"){
        ll tmp = min(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "max"){
        ll tmp = max(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else{
        A.push_back(stoll(S[i]));
      }
    }
    if(A[0] < Y){
      cout << -1 << "\n";
      return 0;
    }
  }
  ll l = -1, r = 100000000000005LL;
  while(1){
    if(l + 1 == r)break;
    ll c = (l + r) / 2;
    vector<ll> A;
    REP(i, 0, Q){
      if(S[i] == "X"){
        A.push_back(c);
      }else if(S[i] == "+"){
        ll tmp = A[ssize(A)-1] + A[ssize(A)-2];
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "min"){
        ll tmp = min(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "max"){
        ll tmp = max(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else{
        A.push_back(stoll(S[i]));
      }
    }
    // cerr << c << " " << A[0] << "\n";
    if(Y <= A[0]){
      r = c;
    }else{
      l = c;
    }
    // cerr << "l " << l << " r " << r << "\n";
  }
  {
    vector<ll> A;
    REP(i, 0, Q){
      if(S[i] == "X"){
        A.push_back(r);
      }else if(S[i] == "+"){
        ll tmp = A[ssize(A)-1] + A[ssize(A)-2];
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "min"){
        ll tmp = min(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else if(S[i] == "max"){
        ll tmp = max(A[ssize(A)-1], A[ssize(A)-2]);
        A.pop_back();
        A.pop_back();
        A.push_back(tmp);
      }else{
        A.push_back(stoll(S[i]));
      }
    }
    if(A[0] == Y){
      cout << r << "\n";
    }else{
      cout << -1 << "\n";
    }
  }
  return 0;
}
/*
  File : ~/yukicoder/midoriika_3rd/I.cpp
  Date : 2024/10/12
  Time : 15:15:17
*/