#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,n) for(int i=0;i<n;i++)
#define Pr pair<ll,ll>
#define Tp tuple<int,int,int>
#define all(v) v.begin(),v.end()
#define riano_ std::ios::sync_with_stdio(false);std::cin.tie(nullptr)
using Graph = vector<vector<ll>>;

const ll mod = 8e18;
template<uint64_t mod>
struct modint{
    uint64_t val;
    constexpr modint(const int64_t val_=0) noexcept:val((val_%int64_t(mod)+int64_t(mod))%int64_t(mod)){}
    constexpr modint operator-() const noexcept{
        return modint(*this)=mod-val;
    }
    constexpr modint operator+(const modint rhs) const noexcept{
        return modint(*this)+=rhs;
    }
    constexpr modint operator-(const modint rhs) const noexcept{
        return modint(*this)-=rhs;
    }
    constexpr modint operator*(const modint rhs) const noexcept{
        return modint(*this)*=rhs;
    }
    constexpr modint operator/(const modint rhs) const noexcept{
        return modint(*this)/=rhs;
    }
    constexpr modint &operator+=(const modint rhs) noexcept{
        val+=rhs.val;
        val-=((val>=mod)?mod:0);
        return (*this);
    }
    constexpr modint &operator-=(const modint rhs) noexcept{
        val+=((val<rhs.val)?mod:0);
        val-=rhs.val;
        return (*this);
    }
    constexpr modint &operator*=(const modint rhs) noexcept{
        val=val*rhs.val%mod;
        return (*this);
    }
    constexpr modint &operator/=(modint rhs) noexcept{
        uint64_t ex=mod-2;
        modint now=1;
        while(ex){
            now*=((ex&1)?rhs:1);
            rhs*=rhs,ex>>=1;
        }
        return (*this)*=now;
    }
    modint & operator++(){
        val++;
        if (val == mod) val = 0;
        return *this;
    }
    modint operator++(int){
        modint<mod> res = *this;
        ++*this;
        return res;
    }
    constexpr bool operator==(const modint rhs) noexcept{
        return val==rhs.val;
    }
    constexpr bool operator!=(const modint rhs) noexcept{
        return val!=rhs.val;
    }
    friend constexpr ostream &operator<<(ostream& os,const modint x) noexcept{
        return os<<(x.val);
    }
    friend constexpr istream &operator>>(istream& is,modint& x) noexcept{
        uint64_t t;
        is>>t,x=t;
        return is;
    }
};
typedef modint<mod> mint;

vector<ll> convert(vector<ll> a){
    vector<ll> res;
    int N = a.size();
    ll acm = 0;
    rep(i,N-1){
        a[i+1] += acm;
        if(a[i+1]<a[i]){
            a[i+1] += 3; acm += 3;
        }
    }
    rep(i,N-2){
        if(a[i+1]-a[i]==a[i+2]-a[i+1]){
            res.push_back(a[i+1]-a[i]);
        }
        else res.push_back(0);
    }
    return res;
}

int main() {
    riano_; ll ans = 0;
    ll N; cin >> N;
    N = N*2+1;
    vector<ll> a;
    rep(i,N){
        ll b; cin >> b;
        a.push_back(b);
    }
    if(N==1){
        cout << a[0] << endl; return 0;
    }
    if(N==3){
        cout << convert(a)[0] << endl; return 0;
    }
    auto v = convert(convert(a));
    N -= 4;
    ans = v[N-1];
    rep(i,N){
        if(i%2==1){
            if(v[i]!=0){
                cout << 0 << endl; return 0;
            }
        }
        else{
            if((N-1-i)%4==0){
                if(v[i]!=ans){
                    cout << 0 << endl; return 0;
                }
            }
            else{
                if(v[i]!=(3^ans)){
                    cout << 0 << endl; return 0;
                }
            }
        }
    }
    cout << ans << endl;
}