#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
const int MAXM = 5e5 + 10;
const int INF = 2147483647;
const int MOD = 1e9 + 7;
long long int a[MAXN], ans, lmax[MAXN], rmax[MAXN];
int n, k;
stack<long long int> stk;
void getMax(int n) {
  while (!stk.empty()) {
    stk.pop();
  }
  stk.push(1);
  a[n + 1] = LONG_LONG_MAX;
  for (int i = 2; i <= n + 1; ++i) {
    if (a[i] <= a[stk.top()]) {
      stk.push(i);
      lmax[i] = 0;
    } else {
      while (!stk.empty() && a[i] >= a[stk.top()]) {
        rmax[stk.top()] = i - stk.top() - 1;
        lmax[i] = lmax[stk.top()] + i - stk.top();
        stk.pop();
      }
      stk.push(i);
    }
  }
}
void solve(int now) {
  long long int minn = min(lmax[now], rmax[now]),
                maxn = max(lmax[now], rmax[now]);
  long long int nowk = k, nxtk = 1, d = k - 1, sum = 0, num;
  if (minn >= k) {
    nxtk = ((minn + 1 - k) / d) * d + k;
    num = (nxtk - nowk) / d + 1;
    if (nxtk >= nowk) {
      sum += ((nowk + nxtk) * num) / 2;
    }
  }
  if (maxn >= k) {
    nowk = nxtk + d;
    nxtk = ((maxn + 1 - k) / d) * d + k;
    num = (nxtk - nowk) / d + 1;
    if (nxtk >= nowk) {
      sum += (minn + 1) * num;
      sum %= MOD;
    }
  }
  long long int p = minn + maxn + 1;
  if (p >= k) {
    nowk = nxtk + d;
    nxtk = ((p - k) / d) * d + k;
    if (nxtk >= nowk) {
      nowk = p - nowk + 1;
      nxtk = p - nxtk + 1;
      swap(nowk, nxtk);
      num = (nxtk - nowk) / d + 1;
      sum += ((nowk + nxtk) * num) / 2;
    }
  }
  sum %= MOD;
  ans += sum * a[now];
  ans %= MOD;
}
void ceshi() {
  for (int i = 1; i <= n; ++i) {
    i == n ? printf("%I64d\n", lmax[i]) : printf("%I64d ", lmax[i]);
  }
  for (int i = 1; i <= n; ++i) {
    i == n ? printf("%I64d\n", rmax[i]) : printf("%I64d ", rmax[i]);
  }
  printf("\n");
}
int main() {
  scanf("%d%d", &n, &k);
  for (int i = 1; i <= n; ++i) {
    scanf("%I64d", &a[i]);
  }
  getMax(n);
  for (int i = 1; i <= n; ++i) {
    solve(i);
  }
  printf("%I64d\n", ans);
  return 0;
}
