#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef vector<VL> VVL;
typedef long long LL;
#define all(a) (a).begin(), (a).end()
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define ALL(a)  (a).begin(),(a).end()
#define pb push_back

int A[200000],q;

int g(string s){
  int n=s.size();
  int a=0;
  rep(i,n){
    a=a*10+s[i]-'0';
  }return a;
}

LL f(LL x){
  VL B;
  rep(i,q){
    /*if(x==0){cout<<'!';
      for(int it : B){cout<<it<<' ';}
    }cout<<endl;
    */
    int m=B.size();
    if(A[i]==-10){B.pb(x);}
    if(A[i]>0){B.pb(A[i]);}
    if(A[i]==-1){
      B[m-2]+=B[m-1];B.pop_back();
    }
    if(A[i]==-2){
      B[m-2]=max(B[m-2],B[m-1]);B.pop_back();
    }
    if(A[i]==-3){
      B[m-2]=min(B[m-2],B[m-1]);B.pop_back(); 
    }
  }
  return B[0];
}

int main() {
  cin>>q;
  LL y;cin>>y;
  int m=0;
  rep(i,q){
    string s;cin>>s;
    //cout<<s<<endl;
    if(s=="+"){A[i]=-1;}
    else if(s=="max"){A[i]=-2;}
    else if(s=="min"){A[i]=-3;}
    else if(s=="X"){A[i]=-10;}
    else{A[i]=g(s);}
  }
  //cout<<f(0)<<endl;
  if(f(2*y)<y){cout<<-1<<endl; return 0;}
  if(f(0)==y){cout<<0<<endl; return 0;}
  LL l=0,r=2*y,t;
  while(r-l>1){
    t=(r+l)/2;
    if(f(t)>=y){r=t;}
    else{l=t;}
  }
  //cout<<f(0)<<endl;
  if(f(r)!=y){r=-1;}
  cout<<r<<endl;
}