Kevin Sun wants to move his precious collection of n cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into k boxes of a fixed size. In order to keep his collection safe during transportation, he won't place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection. 

Kevin is a meticulous cowbell collector and knows that the size of his i-th (1 ≤ i ≤ n) cowbell is an integer si. In fact, he keeps his cowbells sorted by size, so si - 1 ≤ si for any i > 1. Also an expert packer, Kevin can fit one or two cowbells into a box of size s if and only if the sum of their sizes does not exceed s. Given this information, help Kevin determine the smallest s for which it is possible to put all of his cowbells into k boxes of size s.

Input

The first line of the input contains two space-separated integers n and k (1 ≤ n ≤ 2·k ≤ 100 000), denoting the number of cowbells and the number of boxes, respectively.

The next line contains n space-separated integers s1, s2, ..., sn (1 ≤ s1 ≤ s2 ≤ ... ≤ sn ≤ 1 000 000), the sizes of Kevin's cowbells. It is guaranteed that the sizes si are given in non-decreasing order.

Output

Print a single integer, the smallest s for which it is possible for Kevin to put all of his cowbells into k boxes of size s.

Examples

Input

2 1
2 5


Output

7


Input

4 3
2 3 5 9


Output

9


Input

3 2
3 5 7


Output

8

Note

In the first sample, Kevin must pack his two cowbells into the same box. 

In the second sample, Kevin can pack together the following sets of cowbells: {2, 3}, {5} and {9}.

In the third sample, the optimal solution is {3, 5} and {7}.
#include <bits/stdc++.h>
using namespace std;
bool deb_mode = 0;
class debugger {
  vector<string> vars;

 public:
  template <typename T>
  debugger &operator,(const T v) {
    stringstream ss;
    ss << v, vars.push_back(ss.str());
    return *this;
  }
  void printall() {
    int j = 0, l = vars.size();
    for (int i = 0; i < (l - 1); i++) {
      if (i) cout << ", ";
      for (j; j < vars[l - 1].size(); j++) {
        if (vars[l - 1][j] == ',') {
          j++;
          break;
        }
        cout << vars[l - 1][j];
      }
      cout << " = " << vars[i];
    }
    vars.clear();
  }
} Dbug;
template <typename T1, typename T2>
inline ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << "(" << p.first << "," << p.second << ")";
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  bool first = true;
  os << "{";
  for (unsigned int i = 0; i < v.size(); i++) {
    if (!first) os << ",";
    os << v[i];
    first = false;
  }
  return os << "}";
}
template <typename T>
inline ostream &operator<<(ostream &os, const set<T> &v) {
  bool first = true;
  os << "{";
  for (typename set<T>::const_iterator ii = v.begin(); ii != v.end(); ++ii) {
    if (!first) os << ",";
    os << *ii;
    first = false;
  }
  return os << "}";
}
template <typename T1, typename T2>
inline ostream &operator<<(ostream &os, const map<T1, T2> &v) {
  bool first = true;
  os << "{";
  for (typename map<T1, T2>::const_iterator ii = v.begin(); ii != v.end();
       ++ii) {
    if (!first) os << ",";
    os << *ii;
    first = false;
  }
  return os << "}";
}
template <typename T>
T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <typename T>
T BigMod(T b, T p, T m) {
  if (p == 0) return 1;
  if (p % 2 == 0) {
    T s = BigMod(b, p / 2, m);
    return ((s % m) * (s % m)) % m;
  }
  return ((b % m) * (BigMod(b, p - 1, m) % m)) % m;
}
template <typename T>
T ModInv(T b, T m) {
  return BigMod(b, m - 2, m);
}
template <class T>
inline void read(T &x) {
  bool Minus = 0;
  char c;
  for (c = getchar(); c <= 32; c = getchar())
    ;
  if (c == '-') Minus = 1, c = getchar();
  for (x = 0; c > 32; c = getchar()) x = x * 10 + c - '0';
  if (Minus) x = -x;
}
char getc() {
  char c;
  for (c = getchar(); c <= 32; c = getchar())
    ;
  return c;
}
int CI(int &_x) { return scanf("%d", &_x); }
int CI(int &_x, int &_y) { return scanf("%d %d", &_x, &_y); }
int CI(int &_x, int &_y, int &_z) { return scanf("%d %d %d", &_x, &_y, &_z); }
int CI(int &_a, int &_b, int &_c, int &_d) {
  return scanf("%d %d %d %d", &_a, &_b, &_c, &_d);
}
template <class T>
string toString(T n) {
  ostringstream oss;
  oss << n;
  return oss.str();
}
int toInt(string s) {
  int r = 0;
  istringstream sin(s);
  sin >> r;
  return r;
}
long long int toLong(string s) {
  long long int r = 0;
  istringstream sin(s);
  sin >> r;
  return r;
}
int dr8[8] = {+1, -1, +0, +0, +1, -1, -1, +1};
int dc8[8] = {+0, +0, -1, +1, +1, +1, -1, -1};
int dr4[4] = {+0, +0, +1, -1};
int dc4[4] = {-1, +1, +0, +0};
int kn8r[8] = {+1, +2, +2, +1, -1, -2, -2, -1};
int kn8c[8] = {+2, +1, -1, -2, -2, -1, +1, +2};
const double EPS = 1e-9;
const int INF = (1 << 30) - 1;
const long long int LINF = (1ll << 62) - 1;
const int mod = (int)1e9 + 7;
const int MAX = (int)1e5;
int main() {
  int n, k;
  cin >> n >> k;
  int ary[n];
  for (int i = 0; i < n; i++) cin >> ary[i];
  int limit = (n - k) * 2;
  limit = max(0, limit);
  int ans = 0;
  for (int i = 0, j = limit - 1; i < j; i++, j--)
    ans = max(ans, ary[i] + ary[j]);
  for (int i = limit; i < n; i++) ans = max(ans, ary[i]);
  cout << ans << '\n';
  return 0;
}
