#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
const long long Mod = 1e9 + 7;
int n, k;
long long ans;
struct node {
  long long v;
  int p;
  node() {}
  node(int a, long long b) : p(a), v(b) {}
} stk[N];
int L[N], R[N], top;
long long times[N], V[N];
long long calc(int t) {
  if (t < k) return t;
  if (times[t]) return t + times[t];
  long long now = t + calc(t - k + 1);
  return times[t] = now;
}
int main() {
  scanf("%d%d", &n, &k);
  for (int i = k; i <= n; i++) times[i] = calc(i - k + 1) % Mod;
  for (int i = 1; i <= n; i++) scanf("%I64d", &V[i]);
  for (int i = 1; i <= n; i++) {
    while (top > 0 && stk[top].v <= V[i]) --top;
    if (!top) {
      L[i] = 1;
    } else {
      L[i] = stk[top].p + 1;
    }
    stk[++top] = node(i, V[i]);
  }
  top = 0;
  for (int i = n; i >= 1; i--) {
    while (top > 0 && stk[top].v < V[i]) --top;
    if (!top) {
      R[i] = n;
    } else {
      R[i] = stk[top].p - 1;
    }
    stk[++top] = node(i, V[i]);
  }
  for (int i = 1; i <= n; i++) {
    long long now = R[i] - L[i] + 1;
    if (now + 1 >= k) {
      ans = (ans +
             ((times[now] - times[i - L[i]] - times[R[i] - i]) % Mod + Mod) *
                 V[i] % Mod) %
            Mod;
    }
  }
  printf("%I64d\n", ans);
  return 0;
}
