#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5, P = 1e9 + 7;
int n, k, a[N], L[N], R[N];
int get_sum(int a, int b) {
  return (1LL * (a + b) * (b - a + 1) / 2 * (k - 1) + b - a + 1) % P;
}
int find_ans(int l, int p) {
  int en = (l - 1) / (k - 1), ans = en;
  int L = 0, R = en + 1;
  while (L + 1 < R) {
    int mid = L + R >> 1;
    p + mid*(k - 1) <= l ? L = mid : R = mid;
  }
  (ans += (1LL * (en - L) * l + 1LL * L * (p - 1) + get_sum(1, L)) % P) %= P;
  L = 0, R = en + 1;
  while (L + 1 < R) {
    int mid = L + R >> 1;
    p > mid*(k - 1) ? L = mid : R = mid;
  }
  (ans -= (1LL * L * p + get_sum(R, en)) % P) %= P;
  return ans;
}
void readInput() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) cin >> a[i];
}
void prep() {
  for (int i = n - 1; ~i; i--) {
    R[i] = i + 1;
    while (R[i] < n && a[i] > a[R[i]]) R[i] = R[R[i]];
  }
  for (int i = 0; i < n; i++) {
    L[i] = i - 1;
    while (~L[i] && a[i] >= a[L[i]]) L[i] = L[L[i]];
  }
}
void solve() {
  int ans = 0;
  for (int i = 0; i < n; i++)
    (ans += 1LL * a[i] * find_ans(R[i] - L[i] - 1, i - L[i]) % P) %= P;
  cout << (ans + P) % P << endl;
}
int main() {
  ios_base ::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  readInput(), prep(), solve();
  return 0;
}
