#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define pb push_back
#define mp make_pair
#define all(a) begin(a),end(a)
#define FOR(x,val,to) for(int x=(val);x<int((to));++x)
#define FORE(x,val,to) for(auto x=(val);x<=(to);++x)
#define FORR(x,arr) for(auto &x: arr)
#define FORS(x,plus,arr) for(auto x = begin(arr)+(plus); x != end(arr); ++x)
#define FORREV(x,plus,arr) for(auto x = (arr).rbegin()+(plus); x !=(arr).rend(); ++x)
#define REE(s_) {cout<<s_<<'\n';exit(0);}
#define GET(arr) for(auto &i: (arr)) sc(i)
#define whatis(x) cerr << #x << " is " << (x) << endl;
#define e1 first
#define e2 second
#define INF 0x7f7f7f7f
typedef std::pair<int,int> pi;
typedef std::vector<int> vi;
typedef std::vector<std::string> vs;
typedef int64_t ll;
typedef uint64_t ull;
#define umap unordered_map
#define uset unordered_set
using namespace std;
using namespace __gnu_pbds;

#ifdef _WIN32
#define getchar_unlocked() _getchar_nolock()
#define _CRT_DISABLE_PERFCRIT_LOCKS
#endif
template<class L, class R> ostream& operator<<(ostream &os, map<L, R> P) { for(auto const &vv: P)os<<"("<<vv.first<<","<<vv.second<<")"; return os; }
template<class T> ostream& operator<<(ostream &os, set<T> V) { os<<"[";for(auto const &vv:V)os<<vv<<","; os<<"]"; return os; }
template<class T> ostream& operator<<(ostream &os, vector<T> V) { os<<"[";for(auto const &vv:V)os<<vv<<","; os<<"]"; return os; }
template<class L, class R> ostream& operator<<(ostream &os, pair<L, R> P) { os<<"("<<P.first<<","<<P.second<<")"; return os; }
inline int fstoi(const string &str){auto it=str.begin();bool neg=0;int num=0;if(*it=='-')neg=1;else num=*it-'0';++it;while(it<str.end()) num=num*10+(*it++-'0');if(neg)num*=-1;return num;}
inline void getch(char &x){while(x = getchar_unlocked(), x < 33){;}}
inline void getstr(string &str){str.clear(); char cur;while(cur=getchar_unlocked(),cur<33){;}while(cur>32){str+=cur;cur=getchar_unlocked();}}
template<typename T> inline bool sc(T &num){ bool neg=0; int c; num=0; while(c=getchar_unlocked(),c<33){if(c == EOF) return false;} if(c=='-'){ neg=1; c=getchar_unlocked(); } for(;c>47;c=getchar_unlocked()) num=num*10+c-48; if(neg) num*=-1; return true;}template<typename T, typename ...Args> inline void sc(T &num, Args &...args){ bool neg=0; int c; num=0; while(c=getchar_unlocked(),c<33){;} if(c=='-'){ neg=1; c=getchar_unlocked(); } for(;c>47;c=getchar_unlocked()) num=num*10+c-48; if(neg) num*=-1; sc(args...); }
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>; //s.find_by_order(), s.order_of_key() <- works like lower_bound
template<typename T> using ordered_map = tree<T, int, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define N 1000001

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int n,m;
    sc(n,m);
    int a[n];
    GET(a);
    FORR(i,a) --i;
    int cs[n];
    int ros = 0, mal = 0;
    ll bal = 0; //jeśli x nie wykorzystywane, dajesz całe cs dla odpowiedniego
    ll cssum = 0; //stała
    vector<int> vop1[m];
    vector<int> vop2[m];
    vector<int> vnop[m];
    FOR(i,1,n){
        int df = ((a[i]-a[i-1])%m+m)%m;
        cs[i] = df;
        cssum += df;
        if(df < 2) continue;
        if(a[i] > a[i-1]){
            int op = a[i-1]+2;
            int nop = a[i]+1;
            if(op >= nop) continue;
            if(op < m){
                vop1[op].pb(i);
            }
            if(nop < m){
                vnop[nop].pb(i);
            }
        }
        else{
            int op1 = 0;
            int op2 = a[i-1]+2;
            int nop = a[i]+1;
            if(op1 < m){
                vop1[op1].pb(i);
            }
            if(op2 < m){
                vop1[op2].pb(i);
            }
            if(nop < m){
                vnop[nop].pb(i);
            }
        }
    }
    bal = cssum;
    ll ans = bal;
    FOR(k,0,m){
        FORR(i,vnop[k]){
            --mal;
            /* cssum -= cs[i]; */
            --bal; //bo 1 za teleport?
            bal += cs[i];
        }
        bal -= mal;
        bal += ros;
        FORR(i,vop1[k]){
            ++mal;
            /* cssum += cs[i]; */
            ++bal; //bo 1 za teleport?
            bal -= cs[i];
            int df = ((a[i]-k)%m+m)%m;
            bal += df;
        }
        FORR(i,vop2[k]){
            ++ros;
            /* cssum += cs[i]; */
            ++bal; //bo 1 za teleport?
            bal -= cs[i];
            int df = ((a[i]-k)%m+m)%m;
            bal += df;
        }
        ans = min(ans,bal);
    }
    cout << ans << '\n';
}



Measured memory_bytes: 13176