#include <bits/stdc++.h>
using namespace std;
const int p = 1000000007;
int n, k, a[1000005], l[1000005], r[1000005];
stack<int> sta;
int read() {
  char c = getchar();
  int x = 0, f = 1;
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = x * 10 + c - '0';
    c = getchar();
  }
  return x * f;
}
long long calc(int x) {
  int L = l[x] + 1, R = r[x] - 1;
  long long ans = 0, y, z, u;
  if (R - x > x - L) {
    y = (int)floor((x - L) * 1.0 / (k - 1));
    z = (int)ceil((R - x) * 1.0 / (k - 1));
    u = (int)floor((R - L) * 1.0 / (k - 1));
    ans += (z - y - 1) * (x - L + 1);
    ans %= p;
  } else {
    y = (int)floor((R - x) * 1.0 / (k - 1));
    z = (int)ceil((x - L) * 1.0 / (k - 1));
    u = (int)floor((R - L) * 1.0 / (k - 1));
    ans += (z - y - 1) * (R - x + 1);
    ans %= p;
  }
  ans += y * (y + 1) / 2 % p * (k - 1) + y;
  ans %= p;
  ans +=
      (R - L + 1) * (u - z + 1) % p - (z + u) * (u - z + 1) / 2 % p * (k - 1);
  ans %= p;
  return ans;
}
int main() {
  n = read(), k = read();
  for (int i = 1; i <= n; i++) a[i] = read();
  for (int i = 1; i <= n; i++) {
    while (!sta.empty() && a[sta.top()] < a[i]) {
      r[sta.top()] = i;
      sta.pop();
    }
    sta.push(i);
  }
  while (!sta.empty()) {
    r[sta.top()] = n + 1;
    sta.pop();
  }
  for (int i = n; i >= 1; i--) {
    while (!sta.empty() && a[sta.top()] <= a[i]) {
      l[sta.top()] = i;
      sta.pop();
    }
    sta.push(i);
  }
  while (!sta.empty()) {
    l[sta.top()] = 0;
    sta.pop();
  }
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    ans += a[i] * calc(i);
    ans %= p;
  }
  printf("%I64d\n", ans);
  return 0;
}
