#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
int n, k;
int step;
int LEAFOFFSET;
pair<int, int> IT[4000111];
int modval[1000111];
pair<int, int> MAX(pair<int, int> a, pair<int, int> b) {
  if (a.first > b.first)
    return a;
  else
    return b;
}
pair<int, int> getMax(int L, int R) {
  L += LEAFOFFSET;
  R += LEAFOFFSET;
  pair<int, int> ans = MAX(IT[L], IT[R]);
  while (R - L > 1) {
    if (L % 2 == 0) ans = MAX(ans, IT[L + 1]);
    if (R % 2 == 1) ans = MAX(ans, IT[R - 1]);
    L /= 2;
    R /= 2;
  }
  return ans;
}
vector<pair<pair<int, int>, int> > seqA, seqB;
void clearSeq() {
  seqA.clear();
  seqB.clear();
}
void addSeq(int l, int r) {
  int addMore = step - modval[l];
  if (addMore == step) addMore = 0;
  if (l + addMore <= r) {
    if (addMore != 0) {
      seqA.push_back(make_pair(make_pair(modval[l], step - 1), 1));
    }
    l += addMore;
    int dist = r - l + 1;
    int fullHits = dist / step;
    seqA.push_back(make_pair(make_pair(0, step - 1), fullHits));
    if (modval[r] != step - 1) {
      seqA.push_back(make_pair(make_pair(0, modval[r]), 1));
    }
  } else {
    seqA.push_back(make_pair(make_pair(modval[l], modval[r]), 1));
  }
}
void logSeq() {
  int i;
  for (i = 0; i < seqA.size(); i++) {
    seqB.push_back(seqA[i]);
  }
  seqA.clear();
  return;
}
long long countSeq() {
  int i, j;
  int l, r;
  long long ans = 0, val;
  for (i = 0; i < seqA.size(); i++) {
    for (j = 0; j < seqB.size(); j++) {
      l = seqA[i].first.first;
      if (seqB[j].first.first > l) l = seqB[j].first.first;
      r = seqA[i].first.second;
      if (seqB[j].first.second < r) r = seqB[j].first.second;
      if (r >= l) {
        val = (long long)(r - l + 1) * (long long)seqA[i].second;
        if (val >= MOD) val %= MOD;
        val *= (long long)seqB[j].second;
        ans += val;
        if (ans >= MOD) ans %= MOD;
      }
    }
  }
  return ans;
}
long long solve(int L, int R) {
  if (L >= R) return 0LL;
  pair<int, int> res = getMax(L, R);
  int ind = res.second;
  long long ans = solve(L, ind - 1) + solve(ind + 1, R);
  int i;
  clearSeq();
  addSeq(L, ind);
  logSeq();
  addSeq(ind, R);
  long long times = countSeq() - 1;
  if (times < 0) times += MOD;
  ans += times * (long long)res.first;
  return ans % MOD;
}
int main() {
  int i, j;
  scanf("%d %d", &n, &k);
  step = k - 1;
  LEAFOFFSET = 1;
  while (LEAFOFFSET < n) LEAFOFFSET *= 2;
  LEAFOFFSET--;
  modval[0] = 0;
  for (i = 1; i <= n; i++) {
    modval[i] = modval[i - 1] + 1;
    if (modval[i] == step) modval[i] = 0;
  }
  for (i = 1; i <= n; i++) {
    scanf("%d", &IT[i + LEAFOFFSET].first);
    IT[i + LEAFOFFSET].second = i;
  }
  for (i = LEAFOFFSET; i >= 1; i--) {
    IT[i] = MAX(IT[2 * i], IT[2 * i + 1]);
  }
  printf("%lld\n", solve(1, n));
  return 0;
}
