/*Bismillahir Rahmanir Rahim*///{
#include <bits/stdc++.h>
using namespace std;
using ll = long long; using ull = unsigned long long; using ld = long double;
const ll llinf = (1ll<<61)-1;
const double eps = 1e-6, ldeps = 1e-9;
struct Dbg {
static constexpr auto &os = cout;   // replace by cerr in interactive.
template<class C> static auto dud(C *x)->decltype(os << *x, 0);
template<class C> static char dud(...);
template<class C> typename enable_if<sizeof dud<C>(0)!=1, Dbg&>::type operator<<(const C &x) { os << x; return *this; }
template<class C> Dbg &dump(C b, C e) {
    *this << "\n[";
    int cur = 0;
    for (C i = b; i!=e and cur<26; i++, cur++) *this << ", "+2*(i==b) << *i;
    return *this << ']';
}
template<class C> typename enable_if<sizeof dud<C>(0)==1, Dbg&>::type operator<<(const C &x) {
    return dump(begin(x), end(x));
}
template<class C, size_t X> typename enable_if<sizeof(C)!=1, Dbg&>::type operator <<(C (&x)[X]) {
    return dump(begin(x), end(x));
}
template<class B, class C> Dbg &operator <<(const pair<B, C> &x) {
    return *this << '{' << x.first << ", " << x.second << '}';
}
template<class C, size_t Y> struct TP {
    void operator()(Dbg& os, const C &t) { TP<C, Y-1>()(os, t); os << ", " << get<Y-1>(t); }
};
template<class C> struct TP<C, 1> { void operator()(Dbg& os, const C &t) { os << get<0>(t); } };
template<class... C> Dbg& operator<<(const tuple<C...> &t) {
    os << '{', TP<decltype(t), sizeof...(C)>()(*this, t); return *this << '}';
}
Dbg &operator<<(ostream&(*x)(std::ostream&)) { os << x; return *this; }
} dbg;
void err(istringstream *iss) { delete iss; }
template<class C, class... Args> void err(istringstream *iss, const C &val, const Args &... args) {
    string name; *iss >> name; if (name.back()==',') name.pop_back();
    dbg << name << " = " << val << "; ", err(iss, args ...);
}
#define bug(args...) dbg << __LINE__ << ": ", err(new istringstream(string(#args)), args), dbg << endl
#define sl(a) int(strlen(a))
#define sz(a) int(a.size())
int T, Q, cn;//}
const int inf = 1000000007, mxn = 100005;

int n, m, a[mxn];
pair<int, int> cb[mxn];
vector<pair<int, bool> > events[mxn<<1|1];
ll savedCost[mxn];

signed main() { ios::sync_with_stdio(0); cin.tie(NULL); cout.precision(11);
/*
max brightness is 1e5, so we can traverse on favourite brightness x. When a[i]<a[i+1]:
Total number of moves = x out of [a[i]+1, a[i+1]] ? a[i+1]-a[i] : 1+a[i+1]-x.
These two cases can be combined by giving everyone a[i+1]-a[i] at first, then decreasing those for which x is in between.
When a[i]>a[i+1]: create another copy of a[i+1] (and also x if a[i]>x), converted to first case.
*/
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        if (i>1) cb[i] = {a[i-1], a[i]+(a[i]<a[i-1] ? m : 0)};
    }
    ll fixedCost = 0;
    for (int i = 2; i <= n; i++) {
        fixedCost += cb[i].second-cb[i].first;
        if (cb[i].second>cb[i].first+1) events[cb[i].first+2].push_back({i, 0}), events[cb[i].second+1].push_back({i, 1});
    }

    ll costSave = 0, mx = -llinf;
    int cnt = 0;
    for (int i = 1; i <= m<<1; i++) {
        costSave += cnt;
        for (auto &j : events[i]) {
            if (j.second) cnt--, costSave -= cb[j.first].second-cb[j.first].first;
            else cnt++, costSave++;
        }
        savedCost[i>m ? i-m : i] += costSave;
        mx = max(mx, savedCost[i>m ? i-m : i]);
    }
    cout << fixedCost-mx << '\n';
}

Measured memory_bytes: 11648