#include <bits/stdc++.h>
#define X first
#define Y second

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int N = 3e5 + 7;
pair<ll, ll> bit[N];
int n, l, r, b[N], m;
pii a[N];
ll sum , res = LLONG_MAX, f[N];
void upd(int p, ll x, ll y, int n)
{
    while (p<=n)
    {
        bit[p].X+=x;
        bit[p].Y+=y;
        p+=(p&(-p));
    }
}
pair<ll, ll> Get(int p)
{
    ll res = 0, dem = 0;
    while (p>0)
    {
        res+=bit[p].X;
        dem+=bit[p].Y;
        p-=(p&(-p));
    }
    return make_pair(res,dem);
}
int main()
{

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>m;
    for (int i=1; i<=n; i++) cin>>b[i];
    for (int i=1; i<n; i++)
        if (b[i]<b[i+1]) a[i] = make_pair(b[i],b[i+1]); else a[i] = make_pair(b[i],b[i+1] + m);
    n--;
    sort(a+1,  a + 1  + n);
    for (int i=1; i<=n; i++) sum = sum + a[i].Y - a[i].X;
    int j = 0;
    for (int x = 1; x<=m; x++)
    {
        while (j<n && a[j+1].X<x)
        {
            j++;
            upd(a[j].Y, a[j].X, 1, 2*m);
        }
        pair<ll, ll> t = Get(2*m), q = Get(x-1);
        ll cnt = t.Y - q.Y;
        ll sum1 = t.X- q.X;
        ll tmp = sum + sum1 - 1LL*cnt*x + cnt;
        f[x] = tmp;
    }
    for (int i=1; i<=2*m; i++) bit[i] = make_pair(0,0);
    j = 0;
    for (int x = 1; x<=m; x++)
    {
        while (j<n && a[j+1].X<x+m)
        {
            j++;
            upd(a[j].Y, a[j].X, 1, 2*m);
        }
        pair<ll, ll> t = Get(2*m), q = Get(x+m-1);
        ll cnt = t.Y - q.Y;
        ll sum1 = t.X- q.X;
        ll tmp = f[x] + sum1 - 1LL*cnt*(x+m) + cnt;
        f[x] = tmp;
        res = min(res,f[x]);
    }
    cout<<res;
    return 0;
}