#include <bits/stdc++.h>
using namespace std;

int main()
{
    int N, X;
    cin >> N >> X;
    vector<int> S(N);
    for (int i = 0; i < N; i++)
    {
        cin >> S[i];
    }
    long long sum = 0;
    for (int i = 0; i < N; i++)
    {
        sum += X - S[i];
    }
    for (int i = 0; i < N; i++)
    {
        if (S[i] % 2 == 1)
        {
            continue;
        }
        long long tmp = sum - (X - S[i]);
        tmp += X - (S[i] / 2);
        if (tmp == X)
        {
            cout << S[i] / 2;
            return 0;
        }
    }
}