#include <bits/stdc++.h>
using namespace std;
const long long N = 1e5 + 5;
long long mod = 1e9 + 7;
vector<long long> v;
long long n, s;
bool check(long long x) {
  long long sum = 0;
  for (long long i = 0; i < n; i++) {
    sum += (v[i] - x);
  }
  return sum >= s;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cin >> n;
  cin >> s;
  long long z;
  long long sum = 0;
  for (long long i = 0; i < n; i++) cin >> z, v.push_back(z), sum += z;
  if (sum < s) {
    cout << "-1";
    return 0;
  }
  sort(v.begin(), v.end());
  long long l = 0;
  long long r = v[0];
  while (r > l + 1) {
    long long m = (l + r) / 2;
    if (check(m)) {
      l = m;
    } else {
      r = m;
    }
  }
  if (!check(r))
    cout << l << '\n';
  else
    cout << r;
}
