#include <bits/stdc++.h>
inline int min(const int &first, const int &second) {
  return (((second - first) >> (32 - 1)) & (first ^ second)) ^ first;
}
inline int max(const int &first, const int &second) {
  return (((second - first) >> (32 - 1)) & (first ^ second)) ^ second;
}
inline long long min(const long long &first, const long long &second) {
  return (((second - first) >> (64 - 1)) & (first ^ second)) ^ first;
}
inline long long max(const long long &first, const long long &second) {
  return (((second - first) >> (64 - 1)) & (first ^ second)) ^ second;
}
using namespace std;
char string_in_buffer[(int)260];
void fast_scan(int &first) { scanf("%d", &first); }
void fast_scan(long long &first) { scanf("%lld", &first); }
void fast_scan(unsigned long long &first) { scanf("%llu", &first); }
void fast_scan(double &first) { scanf("%lf", &first); }
void fast_scan(long double &first) { scanf("%Lf", &first); }
void fast_scan(char &first) {
  scanf("%c", &first);
  if (first == '\n') {
    fast_scan(first);
  }
}
void fast_scan(string &first) {
  scanf("%s", string_in_buffer);
  first = string(string_in_buffer);
}
template <class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
  fast_scan(p.first);
  fast_scan(p.second);
}
template <class T>
void fast_scan(vector<T> &v) {
  for (auto &first : v) fast_scan(first);
}
void fast_print(const int &first) { printf("%d", first); }
void fast_print(const unsigned int &first) { printf("%u", first); }
void fast_print(const long long &first) { printf("%lld", first); }
void fast_print(const unsigned long long &first) { printf("%llu", first); }
void fast_print(const double &first) { printf("%.15lf", first); }
void fast_print(const long double &first) { printf("%.15Lf", first); }
void fast_print(const char &first) { printf("%c", first); };
void fast_print(const string &first) { printf("%s", first.c_str()); }
void fast_print(const char v[]) { fast_print((string)v); }
template <class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
  fast_print(p.first);
  fast_print(' ');
  fast_print(p.second);
}
template <class T>
void fast_print(const vector<T> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print(' ');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const vector<vector<T>> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print('\n');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const T &v) {
  for (const auto &first : v) {
    fast_print(first);
    fast_print(' ');
  }
}
using namespace std;
namespace smart_io {
string print_start = "";
string sep = " ";
bool first_print = false;
void precall_print() {
  fast_print(print_start);
  print_start = "\n";
  first_print = true;
}
void _print(deque<string>) {}
template <class T, class... Args>
void _print(deque<string> names, T elem, Args... args) {
  if (!first_print) {
    fast_print("\n");
  } else {
    first_print = false;
  }
  fast_print(names.front());
  fast_print(" = ");
  fast_print(elem);
  names.pop_front();
  _print(names, args...);
}
}  // namespace smart_io
template <class T>
ostream &operator,(ostream &os, const T &object) {
  if (!smart_io::first_print) {
    fast_print(smart_io::sep);
  } else {
    smart_io::first_print = false;
  }
  fast_print(object);
  return os;
}
template <class T>
istream &operator,(istream &is, T &object) {
  fast_scan(object);
  return is;
}
namespace escape__from__random__aetuhoetnuhshe {
using namespace std::chrono;
mt19937 rng(duration_cast<milliseconds>(system_clock::now().time_since_epoch())
                .count());
uniform_real_distribution<> prob_dist(0.0, 1.0);
};  // namespace escape__from__random__aetuhoetnuhshe
namespace typedefs {}
namespace numbers_operation {
template <class T>
T floor_mod(T a, T b) {
  if (a >= 0 && b >= 0) return a % b;
  if (a <= 0 && b <= 0) return a % b;
  return abs(b) - (abs(a) % abs(b));
}
}  // namespace numbers_operation
using namespace numbers_operation;
using namespace typedefs;
using namespace escape__from__random__aetuhoetnuhshe;
long long n, L;
vector<long long> v;
struct Elem {
  long long value;
  long long l, r;
};
long long calc_cost(vector<Elem> v) {
  long long r = 0;
  for (long long i = 0; i < ((long long)v.size()); i++) {
    r += v[i].l * v[i].r;
    for (long long j = i + L - 1; j < ((long long)v.size()); j++) {
      r += v[i].l * v[j].r;
    }
  }
  return r;
}
signed main(signed argc, char *argv[]) {
  cin, n, L;
  v.resize(n);
  cin, v;
  vector<Elem> s;
  for (long long i = 0; i < n; i++) s.push_back({v[i], 1, 1});
  long long rez = 0;
  bool change = true;
  while (change) {
    change = false;
    vector<Elem> t;
    vector<Elem> buf;
    long long cur = 2e9;
    for (long long i = 0; i < ((long long)s.size()); i++)
      if (s[i].value != -1) {
        cur = min(cur, s[i].value);
      }
    s.push_back({(long long)-1e9, -1, -1});
    for (long long i = 0; i < ((long long)s.size()); i++) {
      if (s[i].value == cur) {
        buf.push_back(s[i]);
      } else {
        vector<Elem> _new(((long long)buf.size()) / L, {cur + 1, 0, 0});
        if (((long long)buf.size()) < L) {
          for (long long i = 0; i < ((long long)buf.size()); i++) {
            rez += buf[i].l * buf[i].r;
            buf[i].l = buf[i].r = 0;
            buf[i].value = -1;
          }
          _new = buf;
        } else {
          change = true;
          rez += calc_cost(buf);
          long long k = ((long long)buf.size()) % L + 1;
          for (long long j = 0; j < k; j++) _new[0].l += s[j].l;
          for (long long j = 1; j < ((long long)_new.size()); j++)
            _new[j].l += accumulate(
                buf.begin() + k + (j - 1) * L, buf.begin() + k + j * L, 0,
                [](long long value, Elem e) { return value + e.l; });
          reverse(_new.begin(), _new.end());
          reverse(buf.begin(), buf.end());
          for (long long j = 0; j < k; j++) _new[0].r += s[j].r;
          for (long long j = 1; j < ((long long)_new.size()); j++)
            _new[j].r += accumulate(
                buf.begin() + k + (j - 1) * L, buf.begin() + k + j * L, 0,
                [](long long value, Elem e) { return value + e.r; });
          reverse(_new.begin(), _new.end());
          reverse(buf.begin(), buf.end());
          rez -= calc_cost(_new);
        }
        t.insert(t.end(), _new.begin(), _new.end());
        if (s[i].value != -1e9) t.push_back(s[i]);
        buf.clear();
      }
    }
    swap(t, s);
    cur++;
  }
  smart_io::precall_print();
  cout, rez;
}
