#include <bits/stdc++.h>
using namespace std;
const int MAX = 1001000;
int zn[MAX];
int leftBig[MAX];
int rightBig[MAX];
void solve() {
  long long result = 0, base = 1e9 + 7;
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n; ++i) {
    cin >> zn[i];
  }
  vector<pair<int, int> > st;
  st.push_back({int(1e9 + 10000), -1});
  for (int i = 0; i < n; ++i) {
    while (zn[i] > st.back().first) {
      st.pop_back();
    }
    leftBig[i] = st.back().second;
    st.push_back({zn[i], i});
  }
  st.clear();
  st.push_back({int(1e9 + 10000), n});
  for (int i = n - 1; i >= 0; --i) {
    while (zn[i] >= st.back().first) {
      st.pop_back();
    }
    rightBig[i] = st.back().second;
    st.push_back({zn[i], i});
  }
  for (int i = 0; i < n; ++i) {
    int a = i - leftBig[i];
    int b = rightBig[i] - i;
    if (a > b) {
      swap(a, b);
    }
    for (int j = 0; j < a; ++j) {
      int d1 = a - j - 1 - 1;
      int d2 = a - j - 1 + b - 1;
      d1 = d1 / (k - 1);
      if (d1 < 0) d1 = 0;
      d2 = d2 / (k - 1);
      if (d2 < 0) d2 = 0;
      long long t = d2 - d1;
      result = (result + t * zn[i]) % base;
    }
  }
  cout << result << endl;
}
int main() {
  const int inId = 0;
  const int outId = 0;
  if (inId > 0) {
    cerr << "redirect stdin to input " << inId << endl;
    string s = "input";
    s += to_string(inId);
    s += ".txt";
    auto r = freopen(s.c_str(), "r", stdin);
    if (r == nullptr) {
      cerr << "invalid input file " << s;
    }
  }
  if (outId > 0) {
    cerr << "redirect stdout to stdout " << outId << endl;
    string s = "stdout";
    s += to_string(outId);
    s += ".txt";
    auto r = freopen(s.c_str(), "w", stdout);
    if (r == nullptr) {
      cerr << "invalid output file " << s;
    }
  }
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout.precision(10);
  solve();
}
