#include <bits/stdc++.h>
using namespace std;
int q;
unsigned long long y;
vector<int> eg[1<<18];
string s[1<<18];
unsigned long long ev(unsigned long long x){
    stack<unsigned long long> st;
    for(int i=0;i<q;i++){
        if(s[i]=="+"){
            unsigned long long a=st.top();st.pop();
            unsigned long long b=st.top();st.pop();
            st.push(a+b);
        }else if(s[i]=="min"){
            unsigned long long a=st.top();st.pop();
            unsigned long long b=st.top();st.pop();
            st.push(min(a,b));
        }else if(s[i]=="max"){
            unsigned long long a=st.top();st.pop();
            unsigned long long b=st.top();st.pop();
            st.push(max(a,b));
        }else if(s[i]=="X"){
            st.push(x);
        }else{
            st.push(stoll(s[i]));
        }
    }
    return st.top();
}
int main(){
    cin>>q>>y;
    for(int i=0;i<q;i++)cin>>s[i];
    unsigned long long t=ev(0);
    if(t>y){
        cout<<"-1\n";
        return 0;
    }
    if(t==y){
        cout<<"0\n";
        return 0;
    }
    t=ev(100000000000000);
    if(t<y){
        cout<<"-1\n";
        return 0;
    }
    unsigned long long l=0,r=100000000000000;
    while(r-l>1){
        unsigned long long mid=(l+r)/2;
        if(ev(mid)<y)l=mid;
        else r=mid;
    }
    cout<<(ev(r)==y?r:-1)<<endl;
}