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

using ll = long long;
using P = pair<ll, ll>;
const ll INF = (1LL << 61);
ll mod = (ll)1e9 + 7;

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	ll N, X; cin >> N >> X;
	vector<ll>S(N); for (int i = 0; i < N; i++)cin >> S[i];
	vector<ll>a(N);
	for (int i = 0; i < N; i++) {
		a[i] = X - S[i];
	}
	ll sum = 0;
	for (int i = 0; i < N; i++) {
		sum += a[i];
	}
	for (int i = 0; i < N; i++) {
		sum -= a[i];
		if (sum + (X - (S[i] / 2)) == X) {
			cout << S[i] / 2 << endl; return 0;
		}
		sum += a[i];
	}
	return 0;
}