//#include <atcoder/all>
//using namespace atcoder;
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n) for(int i=0; i<n; i++)
#define REPR(i, n) for(int i=n-1; i>=0; i--)
#define FOR(i, m, n) for(int i=m; i<n; i++)
#define ALL(v) v.begin(), v.end()
#define bit(n) (1LL<<(n))
#define FIX(d) fixed << setprecision(d)
#define MAT(tp) vector<vector<tp>>
using P = pair<int, int>;
using LP = pair<ll, ll>;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = 1e9;
const ll LINF = (1LL<<60);

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n; ll x;
  cin >> n >> x;
  vector<ll> s(n);
  REP(i,n) cin >> s[i];
  
  ll sum1 = x*(n-1);
  ll sum2 = 0;
  REP(i,n) sum2 += s[i];
  
  REP(i,n){
    if(sum2-s[i]/2==sum1){
        cout << s[i]/2 << endl;
        break;
    }  
  }
  
  return 0;
}