#ifndef DEBUG
#  define NDEBUG
#endif
#include <iostream>
#include <string>
#include <iterator>
#include <utility>
#include <type_traits>
#include <limits>
#include <cassert>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

// template {{{
// misc {{{
using Z = long long;
[[maybe_unused]]
constexpr Z INF = numeric_limits<Z>::max() / 3;
// }}}

// debug {{{
template <class T>
using enable_if_sequence_t = enable_if_t<
  is_same<
    typename iterator_traits<
      typename remove_cv_t<remove_reference_t<T>>::iterator
    >::iterator_category,
    random_access_iterator_tag>{}>;
#ifdef NDEBUG
# define dump(x)
# define debug if (0)
template <class T>
inline T&& ix(T&& value) { return value; }
template <class T, class Index, class... Indices, class = enable_if_sequence_t<T>>
inline auto&& ix(T&& container, Index index, Indices... indices) {
  return ix(container[index], indices...);
}
#else
# define dump(x) do { \
    cerr << "\e[33m[dump: " << __LINE__ << "] " << (#x) << " = " << x << "\e[0m" << endl; \
  } while (0);
# define debug
template <class T>
inline auto&& ix_impl([[maybe_unused]] int line, [[maybe_unused]] const char* code, T&& value) {
  return value;
}
template <class T, class Index, class... Indices, class = enable_if_sequence_t<T>>
inline auto&& ix_impl(int line, const char* code, T&& container, Index index, Indices... indices) {
  if (index < 0) {
    cerr << "\e[31mix: negative index at line " << line << ", ix(" << code << ")\e[0m" << endl;
    exit(1);
  }
  int size = container.size();
  if (index >= size) {
    cerr << "\e[31mix: index out of range at line " << line << ", ix(" << code << ")\n"
      << "index = " << index << " whereas size = " << size << "\e[0m" << endl;
    exit(1);
  }
  return ix_impl(line, code, container[index], indices...);
}
#define ix(...) ix_impl(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
// }}}

// IO {{{
template <class T, class U>
ostream& operator<< (ostream& os, pair<T, U> p) {
  os << '(' << p.first << ", " << p.second << ')';
  return os;
}
template <class T>
false_type is_container_impl(...);
template <class T, class = typename T::iterator>
true_type is_container_impl(T);
template <class T>
struct is_container : decltype(is_container_impl<T>(declval<T>())) {};
template <>
struct is_container <string> : std::false_type {};
template <class Container, class = enable_if_t<is_container<Container>{}>>
istream& operator>> (istream& is, Container& cont) {
  for (auto& v : cont) is >> v;
  return is;
}
template <class Container, class = enable_if_t<is_container<Container>{}>>
ostream& operator<< (ostream& os, Container const& cont) {
  bool first = true;
  constexpr char sep =
    is_container<typename Container::value_type>{} ? '\n' : ' ';
  for (auto const& v : cont) {
    if (!first) {
      os << sep;
    }
    first = false;
    os << v;
  }
  return os;
}
// }}}
// }}}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  Z n, m;
  cin >> n >> m;
  vector<Z> as(n);
  cin >> as;
  for (auto&& a : as)
    a--;
  vector<Z> constants(m + 1), linears(m + 1);
  for (auto i = 0; i < n - 1; i++) {
    /*
    Z left = ix(as, i), right = ix(as, i + 1);
    if (left < right || left == m - 1) {
      ix(linears, left == m - 1 ? 0 : left + 2)++;
      ix(linears, right + 1)--;
      ix(constants, right + 1) -= right - left - 1;
    }
    else {
      ix(linears, left + 2)++;
      ix(linears, right + 1)--;
      ix(linears, 0)++;
      ix(linears, m)--;
      ix(constants, 0) += m - left - 2;
      ix(constants, m) -= m - left - 2;
      ix(constants, right + 1) -= (right + m) - left - 1;
    }
    */
    if (ix(as, i) + 1 == ix(as, i + 1)) continue;
    Z start = (ix(as, i) + 2) % m, last = ix(as, i + 1) + 1;
    ix(linears, start)++;
    ix(linears, last)--;
    if (start <= last)
      ix(constants, last) -= last - start;
    else {
      ix(linears, 0)++;
      ix(linears, m)--;
      ix(constants, m) -= m - start;
      ix(constants, 0) += m - start;
      ix(constants, last) -= (last + m) - start;
    }
    dump(constants);
    dump(linears);
  }
  partial_sum(begin(linears), end(linears), begin(linears));
  dump(linears);
  for (auto i = 0; i <= m; i++)
    ix(constants, i) += ix(linears, i);
  dump(constants);
  partial_sum(begin(constants), end(constants), begin(constants));
  dump(constants);
  Z max_gain = *max_element(begin(constants), end(constants) - 1);
  Z default_sum = 0;
  for (auto i = 0; i < n - 1; i++)
    default_sum += (ix(as, i + 1) - ix(as, i) + m) % m;
  cout << default_sum - max_gain << endl;
}



Measured memory_bytes: 2560