#include <bits/stdc++.h>
using namespace std;
template <typename T>
void _dbg(const char* _s, T _h) {
  cerr << _s << " = " << _h << "\n";
}
template <typename T, typename... Ts>
void _dbg(const char* _s, T _h, Ts... _t) {
  int _b = 0;
  while (((_b += *_s == '(') -= *_s == ')') != 0 || *_s != ',') cerr << *_s++;
  cerr << " = " << _h << ",";
  _dbg(_s + 1, _t...);
}
const int64_t INF = static_cast<int64_t>(1e9) + 7;
const int64_t LINF = INF * INF;
const int MAXN = static_cast<int>(1e6) + 17;
void solve() {
  int n;
  int64_t second;
  cin >> n >> second;
  vector<int> v(n);
  int64_t sum = 0;
  int right = INF;
  for (auto& el : (v)) {
    cin >> el;
    sum += el;
    right = min(right, el);
  }
  if (sum < second) {
    cout << "-1\n";
    return;
  }
  ++right;
  int left = 0;
  while (right - left > 1) {
    int mid = (left + right) / 2;
    int64_t amount = 0;
    for (int i = 0; i < n; ++i) {
      amount += v[i] - mid;
    }
    if (amount >= second) {
      left = mid;
    } else {
      right = mid;
    }
  }
  cout << left;
}
int main() {
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios_base::sync_with_stdio(false);
  int q = 1;
  for (int i = 0; i < q; ++i) {
    solve();
  }
}
