#include <bits/stdc++.h>
using namespace std;

int ceil(int a, int b) { return (a + b - 1) / b; }

int main() {
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];

  auto f = [&](int x) {
    int s = 0, op_sum = 0;
    for (int i = 0; i < n; i++) {
      int ai = a[i] + s;
      if (ai >= x) continue;
      int op = ceil(x - ai, i + 1);
      op_sum += op;
      s += op * (i + 1);
    }
    return op_sum <= k;
  };

  int lo = -1, hi = 2e9 + 10;
  while (hi - lo > 1) {
    int mi = (lo + hi) / 2;
    if (f(mi))
      lo = mi;
    else
      hi = mi;
  }
  cout << lo << "\n";
}