using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, q) = (c[0], c[1]);
        var a = NList;
        var b = NList;
        var op = new SegOp();
        var lseg = new SegmentTree<int>(n, op);
        var rseg = new SegmentTree<int>(n, op);
        lseg[0] = n - 1;
        rseg[0] = 0;
        for (var i = 0; i < q; ++i)
        {
            var nlseg = new SegmentTree<int>(n, op);
            var nrseg = new SegmentTree<int>(n, op);
            for (var j = 0; j < n; ++j)
            {
                if (a[j] == b[i])
                {
                    var min = Math.Min(lseg.Prod(0, j) - (n - 1 - j), rseg.Prod(j, n) - j);
                    nlseg[j] = min + n - 1 - j;
                    nrseg[j] = min + j;
                }
            }
            lseg = nlseg;
            rseg = nrseg;
        }
        var ans = int.MaxValue;
        for (var i = 0; i < n; ++i) ans = Math.Min(ans, rseg[i] - i);
        WriteLine(ans);
    }
    struct SegOp : ISegmentTreeOperator<int>
    {
        public int Identity => int.MaxValue / 2;

        public int Operate(int x, int y)
        {
            return Math.Min(x, y);
        }
    }

    interface ISegmentTreeOperator<T>
    {
        T Identity { get; }
        T Operate(T x, T y);
    }
    class SegmentTree<T>
    {
        int size;
        int log;
        T[] d;
        ISegmentTreeOperator<T> op;
        void Update(int k)
        {
            d[k] = op.Operate(d[2 * k], d[2 * k + 1]);
        }
        public SegmentTree(int n, ISegmentTreeOperator<T> op)
        {
            this.op = op;
            size = 1;
            while (size < n) size <<= 1;
            log = CountRZero(size);
            d = new T[2 * size];
            for (var i = 0; i < d.Length; ++i) d[i] = op.Identity;
        }
        public SegmentTree(T[] v, ISegmentTreeOperator<T> op)
        {
            this.op = op;
            size = 1;
            while (size < v.Length) size <<= 1;
            log = CountRZero(size);
            d = new T[2 * size];
            for (var i = 0; i < size; ++i) d[i] = op.Identity;
            for (var i = 0; i < v.Length; ++i) d[size + i] = v[i];
            for (var i = size - 1; i >= 1; --i) Update(i);
        }
        int CountRZero(int n)
        {
            var ans = 0;
            while (n % 2 == 0)
            {
                ++ans;
                n >>= 1;
            }
            return ans;
        }
        public T this[int p]
        {
            get { return d[p + size]; }
            set
            {
                p += size;
                d[p] = value;
                for (var i = 1; i <= log; ++i) Update(p >> i);
            }
        }
        public T Prod(int l, int r)
        {
            var sml = op.Identity;
            var smr = op.Identity;
            l += size;
            r += size;
            while (l < r)
            {
                if ((l & 1) != 0) sml = op.Operate(sml, d[l++]);
                if ((r & 1) != 0) smr = op.Operate(d[--r], smr);
                l >>= 1;
                r >>= 1;
            }
            return op.Operate(sml, smr);
        }
        T AllProd() => d[1];
    }
}