#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000006;
int n, k, a[MAXN], b[MAXN];
int bit[MAXN];
void add(int pos, int val) {
  while (pos < MAXN) {
    bit[pos] = max(bit[pos], val);
    pos += pos & (-pos);
  }
}
int sum(int pos) {
  int re = 0;
  while (pos > 0) {
    re = max(re, bit[pos]);
    pos -= pos & (-pos);
  }
  return re;
}
void init() {
  scanf("%d %d", &n, &k);
  for (int i = 1; i <= n; i++) scanf("%d", a + i);
  for (int i = n; i >= 1; i--) {
    add(i, a[i]);
    if (i + k - 1 <= n) {
      b[i] = sum(i + k - 1);
    }
  }
}
struct tup {
  int x, cnt, S;
};
const int MOD = 1e9 + 7;
void push(vector<tup> &sta, int x) {
  int cnt = 1;
  while (sta.size() && sta.back().x <= x) {
    cnt += sta.back().cnt;
    sta.pop_back();
  }
  tup o = {x, cnt, int((long long)x * cnt % MOD)};
  if (sta.size()) {
    o.S += sta.back().S;
    o.S %= MOD;
  }
  sta.push_back(o);
}
vector<tup> sta[MAXN];
int main() {
  init();
  long long ans = 0;
  for (int i = n - k + 1; i >= 1; i--) {
    push(sta[i % (k - 1)], b[i]);
    ans += sta[i % (k - 1)].back().S;
  }
  cout << ans % MOD << '\n';
}
