#include <stdio.h>

int main () {
  int n = 0;
  long long k = 0LL;
  long long a[100000] = {};
  
  int res = 0;
  
  long long ans[2] = { 0LL, 1000000000000000LL };
  
  res = scanf("%d", &n);
  res = scanf("%lld", &k);
  for (int i = 0; i < n; i++) {
    res = scanf("%lld", a+i);
  }
  
  while (ans[1]-ans[0] > 1LL) {
    long long nxt = (ans[0]+ans[1])/2LL;
    long long cnt = 0LL;
    long long sum = 0LL;
    for (int i = 0; i < n; i++) {
      if (a[i]+sum < nxt) {
        long long tmp = 1LL+(nxt-a[i]-sum-1LL)/((long long)(i+1));
        cnt += tmp;
        sum += tmp*((long long)(i+1));
      }
    }
    if (cnt <= k) {
      ans[0] = nxt;
    } else {
      ans[1] = nxt;
    }
  }
  
  printf("%lld\n", ans[0]);
  return 0;
}