#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ull=unsigned long long;
constexpr int MOD=998244353;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep2(i,l,r) for(int i=(l);i<(int)(r);i++)
#define all(v) v.begin(),v.end()

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int Q;
  ll Y;
  cin>>Q>>Y;
  vector<string> A(Q);
  for(auto &i:A)cin>>i;
  auto f=[A](ll X){
    stack<ll,vector<ll>> a;
    for(auto i:A){
      if(i=="max"){
        ll x=a.top();
        a.pop();
        ll y=a.top();
        a.pop();
        a.push(max(x,y));
      }else if(i=="min"){
        ll x=a.top();
        a.pop();
        ll y=a.top();
        a.pop();
        a.push(min(x,y));
      }else if(i=="+"){
        ll x=a.top();
        a.pop();
        ll y=a.top();
        a.pop();
        a.push(x+y);
      }else if(i=="X"){
        a.push(X);
      }else{
        a.push(stoll(i));
      }
    }
    return a.top();
  };
  ll ng=-1,ok=Y;
  while(ok-ng>1){
    ll mid=(ok+ng)/2;
    if(f(mid)>=Y)ok=mid;
    else ng=mid;
  }
  if(f(ok)==Y)cout<<ok<<'\n';
  else cout<<"-1\n";
}