#include <iostream>

using namespace std;

const int N = 114514;

long long a[N], n, k;

int check(long long x) {
  long long now = 0, cnt = 0;
  for(int i = 1; i <= n; i++) {
    if(a[i] + now < x) {
      long long m = (x - (a[i] + now) + i - 1) / i;
      cnt += m;
      now += m * i;
    }
  }
  return cnt <= k;
}

int main() {
  cin >> n >> k;
  for(int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  long long l = 0, r = 1145141919810114514;
  while(l < r) {
    long long mid = (l + r) / 2;
    if(check(mid + 1)) {
      l = mid + 1;
    } else {
      r = mid;
    }
  }
  cout << l;
  return 0;
}