#include <bits/stdc++.h>
using namespace std;
bool comp(pair<long long, long long> p1, pair<long long, long long> p2) {
  return p1.second < p2.second;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long n, k;
  cin >> n >> k;
  k--;
  vector<long long> v(n + 1);
  vector<long long> left(n + 1);
  vector<long long> right(n + 1);
  stack<long long> st;
  for (long long i = 1; i <= n; i++) {
    cin >> v[i];
  }
  for (long long i = 1; i <= n; i++) {
    while (!st.empty() && v[st.top()] < v[i]) {
      right[st.top()] = i - 1;
      st.pop();
    }
    st.push(i);
  }
  while (!st.empty()) {
    right[st.top()] = n;
    st.pop();
  }
  for (long long i = n; i >= 1; i--) {
    while (!st.empty() && v[st.top()] <= v[i]) {
      left[st.top()] = i + 1;
      st.pop();
    }
    st.push(i);
  }
  while (!st.empty()) {
    left[st.top()] = 1;
    st.pop();
  }
  vector<long long> cl(n + 1), fl(n + 1);
  vector<long long> ccl(n + 1, 0), cfl(n + 1, 0);
  long long csf = 0, csc = 0;
  for (long long i = 1; i <= n; i++) {
    csf += i / k;
    fl[i] = csf;
    csc += (i + k - 1) / k;
    cl[i] = csc;
  }
  long long ans = 0;
  for (long long i = 1; i <= n; i++) {
    long long l1 = i - left[i];
    long long l2 = max((long long)1, i - right[i] + k);
    long long lans = 0;
    if (l2 <= l1) {
      lans -= (cl[l1] - cl[l2 - 1]);
      long long r1 = right[i] - left[i];
      long long r2 = right[i] - i + 1;
      lans += (fl[r1] - fl[r2 - 1]);
      lans += l1 - l2 + 1;
      lans = lans % 1000000007;
      ans += lans * v[i];
      ans = ans % 1000000007;
    }
    ans += ((right[i] - i) / (k)) * v[i];
    ans = ans % 1000000007;
  }
  cout << ans;
  return 0;
}
