#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
template<class T> bool chmin(T& a,T b){if(a>b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a,T b){if(a<b) {a = b; return true;} return false;}
#define rep(i,n) for(int i=0;i<(n);i++)
#define drep(i,n) for(int i=(n)-1;i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define debug(x)  cerr << #x << " = " << (x) << endl;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N,X;
    cin >> N >> X;
    vec<ll> A(N),S(N);
    rep(i,N){
        cin >> S[i];
        A[i] = X-S[i];
    }
    ll sum = accumulate(all(A),0LL);
    rep(i,N) if(S[i]%2==0){
        ll now = X-S[i]/2-A[i];
        if(sum+now==X){
            cout << S[i]/2 << "\n";
            return 0;
        }
    }
}