#include <bits/stdc++.h>
using namespace std;
void in() { return; }
template <typename T, typename... Types>
void in(T &a, Types &...b) {
  cin >> (a);
  in(b...);
}
void o() { return; }
template <typename T, typename... Types>
void o(T a, Types... b) {
  cout << (a);
  cout << ' ';
  o(b...);
}
bool sortin(const pair<long long int, long long int> &e,
            const pair<long long int, long long int> &f) {
  return (e.first < f.first);
}
bool POT(long long int x) { return x && (!(x & (x - 1))); }
long long int i, j, k, l, m, n, p, q, r, a, b, c, x, y, z, ts, mn = 1e18,
                                                               mod = 1e9 + 7;
long long int ar[250005], br[250005], xr[250005], tem[250005];
int main() {
  {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
  };
  in(n, m);
  for (long long int i = 0; i <= n - 1; i++) {
    in(ar[i]);
    c += ar[i];
  }
  if (c < m) {
    o(-1);
    return 0;
  }
  sort(ar, ar + n);
  x = c - ar[0] * n;
  if (x >= m) {
    o(ar[0]);
    return 0;
  }
  p = (m - x + n - 1) / n;
  o(ar[0] - p);
}
