#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define xprintf(fmt,...) fprintf(stderr,fmt,__VA_ARGS__)
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(auto cnt=0ll;cnt<(l);++cnt)
#define iterate(cnt,b,e) for(auto cnt=(b);cnt!=(e);++cnt)
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2> ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }
template<typename iterator> inline size_t argmin(iterator begin, iterator end) { return distance(begin, min_element(begin, end)); }
template<typename iterator> inline size_t argmax(iterator begin, iterator end) { return distance(begin, max_element(begin, end)); }
template<typename T> T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> T& minset(T& to, const T& val) { return to = min(to, val); }

mt19937_64 randdev(8901016);
inline ll rand_range(ll l, ll h) {
    return uniform_int_distribution<ll>(l, h)(randdev);
}

#ifdef __MAI
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
#ifdef __VSCC
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        inline MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
            return *this;
        }
        template<typename IT> void in(IT begin, IT end) {
            for (auto it = begin; it != end; ++it) *this >> *it;
        }
    };
}
MaiScanner scanner;


ll m, n, kei;

ll aa[200010];
ll imos[200010];
ll taihen[200010];

ll result[100010];


// ll simulate(ll fav) {
//     //printf("begin FAV:%d\n",fav);
//     ll count = 0;
//     ll a = aa[0];
//     iterate(i, 1, n) {
//         ll b = aa[i];
//         ll v = b - a;
//         if (v < 0) v = b - (a - m);
//         ll w = b - fav;
//         if (w < 0) w = b - (fav - m);
// 
//         ++w; // favボタンを押した
// 
//         count += min(v, w);
// 
//         //printf("%d -> %d; ctrl:%d <= %d vs %d\n",a,b,min(v, w),v,w);
//         a = b;
//     }
//     //printf("fin\n");
//     return count;
// }


int main() {

    scanner >> n >> m;

    repeat(i, n) {
        scanner >> aa[i];
        --aa[i];
    }

    ll sum = 0;
    iterate(i, 1, n) {
        int curr = aa[i];
        int prev = aa[i - 1];

        if (curr < prev)
            curr += m;

        sum += curr - prev;
        imos[prev + 1]++;
        imos[curr]--;
        taihen[curr] += curr - prev - 1;
    }
    ll imos_iter = 0;
    ll diff = 0;
    repeat(i, 200005) {
        diff += imos_iter;
        result[i%m] += diff;

        imos_iter += imos[i];
        diff -= taihen[i];
    }

    ll best = 0;
    repeat(i, m) { maxset(best, result[i]); }

    cout << sum - best << endl;


    //ll str_best = 1e12;
    //repeat(i, m) { minset(str_best, simulate(i)); }
    //cout << str_best << endl;

    return 0;
}

Measured memory_bytes: 4224