#pragma GCC optimize("Ofast") // ������������ ���������, �� ��� ������
#pragma GCC optimize("no-stack-protector") //�����
#pragma GCC optimize("unroll-loops") // � ���� ���� ��� �� 100 �� ������ ����� � ��������� �� ��� � 100 ��� �� ������ ��������
#pragma GCC target("sse,sse2,sse3,ssse3,popcnt,abm,mmx,tune=native") // ��� ����� ����� �� ��� 03 02 ��������� � ������ ������� �������� ��� ���� ������������
#pragma GCC optimize("fast-math")
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <stack>
#include <iomanip>
#include <fstream>
#include <string>
#include <set>
#include <deque>
#include <queue>
#include <map>
#include <bitset>
#include <random>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <cassert>

using namespace std;

typedef long long ll;
typedef short sh;
typedef unsigned long long ull;
typedef long double ld;
typedef string str;
//typedef __int128 ultraint;
#define sqrt sqrtl
#define F first
#define S second
#define endl '\n'
#define all(vc666) vc666.begin(), vc666.end()
#define allr(vc666) vc666.rbegin(), vc666.rend()
#define int long long
#define degug(x) cerr (#x) << " " << (x) << endl;

const ll INF = 3e12;
const ll inf = 1e12 + 7;
const ll ONE = 1;
const ll mod = 1e9 + 7;
const ll m1 = 1e9 + 575179;
const ll m2 = 1e9 + 87;
const ll LG = 19;
const ll k = 347;
ld EPS = 1e-7;
ld PI = 3.1415926535897932384;
ld phi = (sqrt(5) + 1.0) / 2.0;
mt19937_64 gen(rand());

struct Node {
    int mn = INF, push = 0, id = -1;
};
struct SegTree {
    vector <Node> t;
    int n;
    SegTree(int _n) {
        n = 4 * _n;
        t.resize(n);
    }
    void unite(const Node& l, const Node& r, Node& m) {
        if (l.mn < r.mn) {
            m.mn = l.mn;
            m.id = l.id;
        }
        else {
            m.mn = r.mn;
            m.id = r.id;
        }
        m.push = 0;
    }
    void pushUP(int v) {
        t[v].mn += t[v].push;
        if (2 * v + 1 < n) {
            t[2 * v].push += t[v].push;
            t[2 * v + 1].push += t[v].push;
        }
        t[v].push = 0;
    }
    Node query(int v, int tl, int tr, int l, int r) {
        pushUP(v);
        if (tr < l || tl > r) {
            return { INF, 0, -1 };
        }
        else if (l <= tl && r >= tr) {
            return t[v];
        }
        else {
            int m = (tl + tr) / 2;
            Node L = query(2 * v, tl, m, l, r), R = query(2 * v + 1, m + 1, tr, l, r), M;
            unite(L, R, M);
            unite(t[v * 2], t[v * 2 + 1], t[v]);
            return M;
        }
    }
    void update(int v, int tl, int tr, int l, int r, int boost) {
        pushUP(v);
        if (tl > r || tr < l) {
            return;
        }
        else {
            if (tl >= l && tr <= r) {
                t[v].push += boost;
                pushUP(v);
            }
            else {
                int tm = (tl + tr) / 2;
                update(v * 2, tl, tm, l, r, boost);
                update(v * 2 + 1, tm + 1, tr, l, r, boost);
                unite(t[v * 2], t[v * 2 + 1], t[v]);
            }
        }
    }
    void build(int v, int tl, int tr, vector <int>& w) {
        if (tl == tr) {
            t[v].mn = w[tl];
            t[v].id = tl;
        }
        else {
            int tm = (tl + tr) / 2;
            build(2 * v, tl, tm, w);
            build(2 * v + 1, tm + 1, tr, w);
            unite(t[v * 2], t[v * 2 + 1], t[v]);
        }
    }
};

void solve() {
    int n, q, i, j, s, t;
    cin >> n >> q >> s >> t;
    s--, t--;
    vector <int> p(q);
    vector <int> w(n);
    for (i = 0; i < q; i++) {
        cin >> p[i];
        p[i]--;
    }
    for (i = 0; i < n; i++) {
        w[i] = inf + i;
    }
    SegTree t1(n), t2(n);
    t1.build(1, 0, n - 1, w);
    reverse(all(w));
    t2.build(1, 0, n - 1, w);
    t1.update(1, 0, n - 1, s, s, abs(p[0] - t) - inf);
    if (s != t) {
        t1.update(1, 0, n - 1, t, t, abs(p[0] - s) - inf);
    }
    t2.update(1, 0, n - 1, s, s, abs(p[0] - t) - inf);
    if (s != t) {
        t2.update(1, 0, n - 1, t, t, abs(p[0] - s) - inf);
    }
    Node res1, res2, el1, el2;
    int u1, u2, ans = INF;
    for (i = 0; i < q - 1; i++) {
        if (p[i + 1] == p[i]) continue;
        res1 = t2.query(1, 0, n - 1, 0, p[i + 1]);
        res2 = t1.query(1, 0, n - 1, p[i + 1], n - 1);
        el1 = t1.query(1, 0, n - 1, p[i], p[i]);
        el2 = t2.query(1, 0, n - 1, p[i], p[i]);
        u1 = res1.mn + (p[i + 1] - res1.id) - (n - res1.id - 1);
        u2 = res2.mn + (res2.id - p[i + 1]) - res2.id;
        t1.update(1, 0, n - 1, p[i], p[i], min(u1, u2) - el1.mn + p[i]);
        t2.update(1, 0, n - 1, p[i], p[i], min(u1, u2) - el2.mn + (n - p[i] - 1));
        t1.update(1, 0, n - 1, 0, p[i] - 1, abs(p[i + 1] - p[i]));
        t1.update(1, 0, n - 1, p[i] + 1, n - 1, abs(p[i + 1] - p[i]));
        t2.update(1, 0, n - 1, 0, p[i] - 1, abs(p[i + 1] - p[i]));
        t2.update(1, 0, n - 1, p[i] + 1, n - 1, abs(p[i + 1] - p[i]));
        if (i == 1) {
            /*for (j = 0; j < n; j++) {
                el1 = t1.query(1, 0, n - 1, j, j);
                cout << el1.mn << " " << el1.id << endl;
            }
            for (j = 0; j < n; j++) {
                el2 = t2.query(1, 0, n - 1, j, j);
                cout << el2.mn << " " << el2.id << endl;
            }
            for (j = 0; j < n; j++) {
                el1 = t1.query(1, 0, n - 1, j, j);
                el2 = t2.query(1, 0, n - 1, j, j);
                assert(el1.mn - el1.id == el2.mn - (n - el2.id - 1));
                cout << el1.mn - el1.id << " " << el2.mn - (n - el2.id - 1) << endl;
            }
            */
        }
    }
    for (i = 0; i < n; i++) {
        el1 = t1.query(1, 0, n - 1, i, i);
        el2 = t2.query(1, 0, n - 1, i, i);
        ans = min(ans, el1.mn - el1.id);
        ans = min(ans, el2.mn - (n - el2.id - 1));
    }
    cout << ans << endl;
}

signed main() {
#ifdef _DEBUG
    freopen("input.txt", "r ", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    //cin >> t;
    while (t--) solve();
}
//Deisgned by skimono