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

int n, k;
vector<long long> a;

long long solve();
bool ch(long long x);

int main() {
  cin >> n >> k;
  a.resize(2 * n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    a[i + n] = a[i];
  }
  cout << solve() << endl;
  return 0;
}

long long solve() {
  long long l = 0, r = 1;
  for (int i = 0; i < n; ++i) r += a[i];
  while (r - l > 1) {
    long long mid = (l + r) >> 1;
    if (ch(mid))
      l = mid;
    else
      r = mid;
  }
  return l;
}
bool ch(long long x) {
  vector<long long> memo(n, -1);
  for (long long i = 0, sum = 0, r = 0; i < n; ++i) {
    while (r < 2 * n && sum < x) sum += a[r++];
    memo[i] = r - i;
    sum -= a[i];
  }
  vector<vector<long long>> dp;
  dp.resize(20, vector<long long>(n));
  dp[0] = memo;
  for (int i = 1; i <= 17; ++i)
    for (int j = 0; j < n; ++j)
      dp[i][j] = dp[i - 1][j] + dp[i - 1][(j + dp[i - 1][j]) % n];
  for (int i = 0; i < n; ++i) {
    long long cnt = 0;
    for (int j = 0; j <= 17; ++j)
      if (k >> j & 1) cnt += dp[j][(i + cnt) % n];
    if (cnt <= n) return 1;
  }
  return 0;
}