#include<bits/stdc++.h>
#include<atcoder/all>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))z
using namespace std;
using namespace atcoder;
using ll = long long;
const ll mod = 998244353;
using mint = modint998244353;
using Graph = vector<vector<pair<int,ll>>>;
const vector<int> dx = {1,0,-1,0}, dy = {0,1,0,-1};

double dist(int x1, int y1, int x2, int y2){
  double res = (x1-x2) * (x1-x2) + (y1-y2) * (y1-y2);
  return sqrt(res);
}

ll f(ll x, vector<string> v){
  int n = v.size();
  vector<ll> a;
  for(int i = 0; i < n; i++){
    if(v[i] == "X")
      a.push_back(x);
    else if(v[i] == "+"){
      ll b = a.back();
      a.pop_back();
      ll c = a.back();
      a.pop_back();
      a.push_back(b+c);
    }
    else if(v[i] == "min"){
      ll b = a.back();
      a.pop_back();
      ll c = a.back();
      a.pop_back();
      a.push_back(min(b,c));
    }
    else if(v[i] == "max"){
      ll b = a.back();
      a.pop_back();
      ll c = a.back();
      a.pop_back();
      a.push_back(max(b,c));
    }
    else{
      ll m = stoi(v[i]);
      a.push_back(m);
    }
  }
  return a.front();
}

int main(){
  // input
  int Q; ll Y;
  cin >> Q >> Y;
  vector<string> S(Q);
  for(int i = 0; i < Q; i++){
    cin >> S[i];
    assert(S[i].size() > 0);
  }
    
  // solve
  ll lo = -1, hi = 4e18;
  while(abs(hi-lo) > 1){
    ll mid = (lo + hi) / 2;
    
    if(f(mid,S) >= Y) hi = mid;
    else lo = mid;
  }
  
  // output
  cout << (hi >= 0 && f(hi,S) == Y ? hi : -1) << endl;
}