import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.io.Closeable;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) throws Exception {
        Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 29);
        thread.start();
        thread.join();
    }

    static class TaskAdapter implements Runnable {
        @Override
        public void run() {
            InputStream inputStream = System.in;
            OutputStream outputStream = System.out;
            FastInput in = new FastInput(inputStream);
            FastOutput out = new FastOutput(outputStream);
            EGuruguru solver = new EGuruguru();
            solver.solve(1, in, out);
            out.close();
        }
    }

    static class EGuruguru {
        public void solve(int testNumber, FastInput in, FastOutput out) {
            int n = in.readInt();
            int m = in.readInt();
            int[] target = new int[n];
            in.populate(target);

            LongBIT aBit = new LongBIT(m * 2 + 1);
            LongBIT bBit = new LongBIT(m * 2 + 1);

            long sum = 0;
            for (int i = 1; i < n; i++) {
                int from = target[i - 1];
                int to = target[i];
                if (to < from) {
                    to += m;
                }
                sum += to - from;
                update(aBit, from + 1, to, 1);
                update(bBit, from + 1, to, -(from + 1));
            }

            int cur = 0;
            long maxReduce = 0;
            for (int i = 1; i <= m; i++) {
                long a1 = aBit.query(i);
                long a2 = aBit.query(i + m);
                long b = bBit.query(i) + bBit.query(i + m);

//            if(sum - estimate(target, i, m) != (a1 * i + a2 * (m + i) + b)){
//                throw new RuntimeException();
//            }

                maxReduce = Math.max(maxReduce, a1 * i + a2 * (m + i) + b);
            }

            out.println(sum - maxReduce);
        }

        public void update(LongBIT bit, int l, int r, long val) {
            bit.update(l, val);
            bit.update(r + 1, -val);
        }

    }

    static class LongBIT {
        private long[] data;
        private int n;

        public LongBIT(int n) {
            this.n = n;
            data = new long[n + 1];
        }

        public long query(int i) {
            long sum = 0;
            for (; i > 0; i -= i & -i) {
                sum += data[i];
            }
            return sum;
        }

        public void update(int i, long mod) {
            if (i <= 0) {
                return;
            }
            for (; i <= n; i += i & -i) {
                data[i] += mod;
            }
        }

        public String toString() {
            StringBuilder builder = new StringBuilder();
            for (int i = 1; i <= n; i++) {
                builder.append(query(i) - query(i - 1)).append(' ');
            }
            return builder.toString();
        }

    }

    static class FastOutput implements AutoCloseable, Closeable, Appendable {
        private StringBuilder cache = new StringBuilder(10 << 20);
        private final Writer os;

        public FastOutput append(CharSequence csq) {
            cache.append(csq);
            return this;
        }

        public FastOutput append(CharSequence csq, int start, int end) {
            cache.append(csq, start, end);
            return this;
        }

        public FastOutput(Writer os) {
            this.os = os;
        }

        public FastOutput(OutputStream os) {
            this(new OutputStreamWriter(os));
        }

        public FastOutput append(char c) {
            cache.append(c);
            return this;
        }

        public FastOutput append(long c) {
            cache.append(c);
            return this;
        }

        public FastOutput println(long c) {
            return append(c).println();
        }

        public FastOutput println() {
            cache.append(System.lineSeparator());
            return this;
        }

        public FastOutput flush() {
            try {
                os.append(cache);
                os.flush();
                cache.setLength(0);
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
            return this;
        }

        public void close() {
            flush();
            try {
                os.close();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        }

        public String toString() {
            return cache.toString();
        }

    }

    static class FastInput {
        private final InputStream is;
        private byte[] buf = new byte[1 << 13];
        private int bufLen;
        private int bufOffset;
        private int next;

        public FastInput(InputStream is) {
            this.is = is;
        }

        public void populate(int[] data) {
            for (int i = 0; i < data.length; i++) {
                data[i] = readInt();
            }
        }

        private int read() {
            while (bufLen == bufOffset) {
                bufOffset = 0;
                try {
                    bufLen = is.read(buf);
                } catch (IOException e) {
                    bufLen = -1;
                }
                if (bufLen == -1) {
                    return -1;
                }
            }
            return buf[bufOffset++];
        }

        public void skipBlank() {
            while (next >= 0 && next <= 32) {
                next = read();
            }
        }

        public int readInt() {
            int sign = 1;

            skipBlank();
            if (next == '+' || next == '-') {
                sign = next == '+' ? 1 : -1;
                next = read();
            }

            int val = 0;
            if (sign == 1) {
                while (next >= '0' && next <= '9') {
                    val = val * 10 + next - '0';
                    next = read();
                }
            } else {
                while (next >= '0' && next <= '9') {
                    val = val * 10 - next + '0';
                    next = read();
                }
            }

            return val;
        }

    }
}



Measured memory_bytes: 46760