#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T bigMod(T p, T e, T M) {
  long long ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p) % M;
    p = (p * p) % M;
  }
  return (T)ret;
}
template <class T>
inline T modInverse(T a, T M) {
  return bigMod(a, M - 2, M);
}
template <class T>
inline T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
inline T lcm(T a, T b) {
  a = abs(a);
  b = abs(b);
  return (a / gcd(a, b)) * b;
}
template <class T>
inline string int2String(T a) {
  ostringstream str;
  str << a;
  return str.str();
}
const int dr[] = {0, 1, 0, -1, -1, 1, 1, -1, -2, -2, 2, 2, -1, -1, 1, 1};
const int dc[] = {1, 0, -1, 0, 1, 1, -1, -1, -1, 1, -1, 1, -2, 2, -2, 2};
void fileIO() {}
int main() {
  long long n, s;
  scanf("%lld%lld", &n, &s);
  vector<long long> v(n);
  long long sum = 0;
  for (int i = int(0); i < int(n); i++) scanf("%lld", &v[i]), sum += v[i];
  if (sum < s) {
    puts("-1");
    return 0;
  }
  sort(v.begin(), v.end(), greater<int>());
  sum = 0;
  for (int i = int(0); i < int(n); i++) {
    sum += v[i] - v.back();
    v[i] = v.back();
    if (sum >= s) {
      printf("%lld\n", v.back());
      return 0;
    }
  }
  long long need = s - sum;
  long long mn = (n + need - 1) / n;
  printf("%lld\n", v.back() - mn);
  return 0;
}
