#include <bits/stdc++.h>
using namespace std;
long long int r[1000005], l[1000005];
long long int A[1000005];
long long int dp[1000005 + 1] = {0};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> A[i];
  r[n - 1] = 0;
  stack<int> s;
  s.push(n - 1);
  for (int i = n - 2; i >= 0; i--) {
    while (!s.empty() && A[s.top()] < A[i]) s.pop();
    if (!s.empty())
      r[i] = s.top() - i - 1;
    else
      r[i] = n - i - 1;
    s.push(i);
  }
  while (!s.empty()) s.pop();
  l[0] = 0;
  s.push(0);
  for (int i = 1; i < n; i++) {
    while (!s.empty() && A[s.top()] <= A[i]) s.pop();
    if (!s.empty())
      l[i] = i - s.top() - 1;
    else
      l[i] = i;
    s.push(i);
  }
  for (int i = k; i <= n; i += (k - 1)) dp[i] = 1;
  for (int i = 1; i <= n; i++) {
    dp[i] += dp[i - 1];
  }
  for (int i = 1; i <= n; i++) dp[i] = (dp[i] + dp[i - 1]) % 1000000007;
  long long int sum = 0;
  long long int temp;
  for (int i = 0; i < n; i++) {
    temp = (dp[l[i] + r[i] + 1] - dp[r[i]] - dp[l[i]]) % 1000000007;
    if (temp < 0) temp += 1000000007;
    sum = (sum + 1LL * temp * A[i]) % 1000000007;
  }
  sum = sum % 1000000007;
  cout << sum << "\n";
}
