#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <sstream>
#include <iostream>
#include <iomanip>
#define _USE_MATH_DEFINES
#include <cmath>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cfloat>
#include <cmath>
#include <ctime>
#include <cstdio>
#include <cassert>
using namespace std;

#define EPS 1e-12
#define ull unsigned long long
#define ll long long
#define VI vector<ll>
#define PII pair<ll, ll> 
#define VVI vector<vector<ll> >
#define REP(i,n) for(int i=0,_n=(n);(i)<(int)_n;++i)
#define RANGE(i,a,b) for(int i=(int)a,_b=(int)(b);(i)<_b;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define ALLR(c) (c).rbegin(), (c).rend()
#define PB push_back
#define MP(a, b) make_pair(a, b)
#define POPCOUNT __builtin_popcount
#define POPCOUNTLL __builtin_popcountll
#define CLEAR(table, v) memset(table, v, sizeof(table));
#define PRINT1(table, D0) REP(d0, D0) cout<<table[d0]<<" "; cout<<"\n";
#define PRINT2(table, D0, D1) REP(d0, D0) { REP(d1, D1) cout<<table[d0][d1]<<" "; cout<<"\n"; }
#define PRINT3(table, D0, D1, D2) REP(d0, D0) { REP(d1, D1) { REP(d2, D2) cout<<table[d0][d1][d2]<<" "; cout<<"\n"; } cout<<"\n"; }
#define UNIFORM_DOUBLE(a, b) (((b-a)*(double)rand()/RAND_MAX)+a) // [a, b) 
#define UNIFORM_LL(a, b) (ll)UNIFORM_DOUBLE(a, b) // [a, b) 
#define IN(v, lo, hi) ((lo)<=(v) && (v)<(hi))
#define DD(v) cout<<#v<<": "<<v<<endl
template <typename T0, typename T1> std::ostream& operator<<(std::ostream& os, const map<T0, T1>& v) { for( typename map<T0, T1>::const_iterator p = v.begin(); p!=v.end(); p++ ){os << p->first << ": " << p->second << " ";} return os; }
template <typename T0, typename T1> std::ostream& operator<<(std::ostream& os, const pair<T0, T1>& v) { os << v.first << ": " << v.second << " "; return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const vector<T>& v) { for( int i = 0; i < (int)v.size(); i++ ) { os << v[i] << " "; } return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const vector<vector<T> >& v) { for( int i = 0; i < (int)v.size(); i++ ) { os << v[i] << endl; } return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const set<T>& v) { vector<T> tmp(v.begin(), v.end()); os << tmp; return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const deque<T>& v) { vector<T> tmp(v.begin(), v.end()); os << tmp; return os; }

#define MOD 1000000007LL
#define INF (1LL<<60)

/*
b〜a間は+0
a+1()〜b(1)間は-1

*/

ll g(ll M, ll pv, ll v) {
	if(pv==v) return 0;
	ll a = pv <= v ? v-pv : v+M-pv;
	return a;
}

ll f(ll M, ll m, ll pv, ll v) {
	if(pv==v) return 0;
	ll a = g(M, pv, v);
	ll b = 1 + (m <= v ? v-m : v+M-m);
	ll rv = min(a, b);
//	DD(m);
//	DD(pv);
//	DD(v);
//	DD(rv);
	return rv;
}

ll naive(ll N, ll M, const VI& w) {
	ll ans = 1LL<<60;
	RANGE(m, 1, M+1) {
		ll lans = 0;
		RANGE(i, 1, N) {
			lans += f(M, m, w[i-1], w[i]);
		}
//		DD(m);
//		DD(lans);
		ans = min(ans, lans);
	}
	return ans;
}

ll solve(ll N, ll M, const VI& w) {
	auto MM = [=](ll val) {
		return (val-1+M)%M+1;
	};

	VI tl(2*M); // [i] : i-1 から i になるときの差分
	ll ans1 = 0;
	ll ansv1 = 0;
	RANGE(i, 1, N) {
		ll v = w[i];
		ll pv = w[i-1];

		// pv -> v
		ll lans1 = f(M, 1, pv, v);
		ans1 += lans1;

		if(pv!=v)
		{
//			VI _tb(2*M);
//			VI& tb = _tb;
			VI& tb = tl;

			ll diff = g(M, pv, v)-f(M, v, pv, v);
			tb[MM(pv+2)]--;
			tb[MM(v+1)]+=1+diff;
			tb[MM(v+2)]+=-diff;

			ll lansv1 = 0;
			if((pv<=v && pv+1<v) || (pv>v && pv+1<v+M)) {
				if(MM(pv+2) <= v) {
					if(MM(pv+2)==1) lansv1 = -1;
				} else {
					lansv1 = -1;
				}
			}
			if(MM(v+1)==1) lansv1 = diff;

			ansv1 += lansv1;
//			DD(pv);
//			DD(v);
//			DD(lans1);
//			DD(lansv1);
			RANGE(m, 1, M+1) {
//				DD(f(M, m, pv, v));
			}
//			DD(tb);
//			ll vv = lans1;
//			ll vvv = lansv1;
//			DD(vv);
//			RANGE(m, 2, M+1) {
//				vvv += tb[m];
//				vv += vvv;
////				DD(vv);
//			}
//			REP(j, tl.size()) tl[j] += tb[j];
		}
	}
//	DD(tl);
//	DD(ans1);
//	DD(ansv1);
	ll ans = ans1;
	ll v = ans1;
	ll vv = ansv1;
	RANGE(m, 2, M+1) {
		vv += tl[m];
		v += vv;
//		DD(v);
		ans = min(ans, v);
	}
	return ans;
}

int main() {
	ios::sync_with_stdio(false);
	ll N,M,v;
	
	if(0)
	{
		N = 2;
		M = 20;
		REP(i, N) {
			RANGE(m0, 1, M+1) RANGE(m1, 1, M+1) {
				VI w(N);
				w[0] = m0;
				w[1] = m1;
				ll ref = naive(N, M, w);
				ll ans = solve(N, M, w);
				DD(m0);
				DD(m1);
				DD(ref);
				DD(ans);
				assert(ref==ans);
			}
		}
	}
	
	while(cin>>N>>M) {
		VI w(N);
		REP(i, N) {
			cin>>w[i];
		}
//		ll ref = naive(N, M, w);
//		DD(ref);

		ll ans = solve(N, M, w);

		cout<<ans<<endl;
//		break;
	}
	
	return 0;
}


Measured memory_bytes: 2560