//####################################################################
//#####In the Name Of Allah,the Most Gracious,the Most Merciful.######
//####################################################################
//############Created by Sazid Rahman Simanto on 3/20/17.#############
//#####Copyright 2017 Sazid Rahman Simanto. All rights reserved.######
//####################################################################

#include <iostream>
#include <string>
#include <sstream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <utility>
#include <bitset>
#include <list>
#include <algorithm>
#include <complex>

using namespace std;

#define MSET(a,x) memset(a,x,sizeof a)
#define FOR(i,x,y) for(int i=(x);i<=(y);i++)
#define FORR(i,x,y) for(int i=(x);i<(y);i++)
#define ROF(i,x,y) for(int i=(y);i>=(x);i--)
#define SQ(x) ((x)*(x))
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define ff first
#define ss second
#define pb push_back
#define inf             1061109567
#define maxn            100010
#define esp             1e-8
#define mod             1000000007
#define ll              long long
#define ull             unsigned long long
#define pii             pair<int,int>
#define pll             pair<ll,ll>
#define read()          freopen("input.txt", "r", stdin)
#define write()         freopen("output.txt", "w", stdout)


typedef pair<int , int> ii;
typedef complex<double> base;
const double PI = acos(- 1);

template <class T> inline T bigmod(T a, T b,T M) {
        ll ret = 1;
        for(; b > 0; b >>= 1) {
                if(b & 1) ret = (ret * a) % M;
                a = (a * a) % M;
        }
        return ret;
}

template <class T> inline T gcd ( T a, T b ) {

        while (b) {
                a = a % b;
                swap ( a, b );
        }
        return a;
}


template <class T> inline T lcm(T a, T b) { return (a / gcd(a, b)) * b; }

template <class T> inline T poww(T a, T b) {
        ll ret = 1;
        for(; b > 0; b >>= 1) {
                if(b & 1) ret = ret * a;
                a = a * a;
        }
        return (T)ret;
}

pii exEuclid(int a, int b) {
        if(b == 0) return pii(1, 0);
        else {
                pii r = exEuclid(b, a % b);
                return pii(r.ss, r.ff - r.ss * (a / b));
        }
}

int modInv(int a, int m) { pii ret = exEuclid(a, m); return ((ret.ff % m) + m ) % m; }



int Set(int N, int pos) {return N = N | (1 << pos);}
int reset(int N, int pos) {return N = N & ~ (1 << pos);}
bool check(int N, int pos) {return (bool) (N & (1 << pos));}

//####################################################################
//##################Template Ends Here################################
//####################################################################
int n, m;
ll arr[maxn], csum[2 * maxn];

int main() {

        //read();
        //ios_base::sync_with_stdio(false); cin.tie(NULL);cout.tie(NULL);
        //write();

        scanf("%d %d", &n, &m);

        FOR(i, 1, n){
                scanf("%lld", &arr[i]);
                arr[i] --;
        }
        ll tmp = 0;
        FOR(i, 2, n){
                int L = arr[i - 1], R = arr[i];
                if(L <= R){
                        tmp += R - L;
                        if(R - L >= 2){
                                R ++;
                                L += 2;
                                csum[L] += 1;
                                csum[R] -= (R - L + 1);
                                csum[R + 1] += (R - L);
                        }
                }
                else{
                        tmp += ((R + m) - L);
                        if((R + m) - L >= 2){
                                R += (m + 1);
                                L += 2;
                                csum[L] += 1;
                                csum[R] -= (R - L + 1);
                                csum[R + 1] += (R - L);
                        }
                }

        }
        FORR(i, 0, m + m){
                csum[i] += csum[i - 1];
        }
        FORR(i, 0, m + m){
                csum[i] += csum[i - 1];
        }
        ll mx = - 1e18;
        FORR(i, 0, m) mx = max(mx, csum[i] + csum[i + m]);
        cout << tmp - mx << endl;

        return 0;

}


Measured memory_bytes: 2560