#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for (int i = 0; i < (int) (n); i++)
#define reps(i, n) for (int i = 1; i <= (int) (n); i++)
#define all(x) (x).begin(), (x).end()
#define uniq(x) (x).erase(unique(all(x)), (x).end())
#define bit(n) (1LL << (n))
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template<typename T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double PI = 3.1415926535897932384626433832795028;
constexpr int DY[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0};
constexpr int DX[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
int sign(int x) { return (x > 0) - (x < 0); }
int gcd(int a, int b) {
    while (b) { swap(a %= b, b); }
    return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
int cdiv(int a, int b) { return (a - 1 + b) / b; }
template<typename T> void fin(T mes) {
    cout << mes << endl;
    exit(0);
}
template<typename T, typename U> bool chmax(T &a, const U &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> bool chmin(T &a, const U &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
    os << "(" << rhs.first << ", " << rhs.second << ")";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const deque<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const set<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
struct setup {
    static constexpr int PREC = 20;
    setup() {
        cout << fixed << setprecision(PREC);
        cerr << fixed << setprecision(PREC);
    };
} setup;

template<typename F> long long discrete_binary_search(long long ok, long long ng, F is_ok) {
    while (abs(ok - ng) > 1) {
        long long mid = (ok + ng) / 2;
        (is_ok(mid) ? ok : ng) = mid;
    }
    return ok;
}

const int INF = 1e11;
int N, Q, A, B;
int x[220000];
signed main() {
    cin >> N >> Q >> A >> B, A--, B--;
    set<pint> s;
    s.emplace(-INF, abs(-INF - A));
    s.emplace(A, 0);
    s.emplace(INF, abs(INF - A));
    int last = B, bias = 0;
    auto get = [](const set<pint> &s, int x) {
        auto p = s.lower_bound({x + 1, -INF});
        pint l = *(prev(p)), r = *p;
        return l.second + (x - l.first) * sign(r.second - l.second);
    };
    rep(i, Q) {
        cin >> x[i], x[i]--;
        int dist = abs(x[i] - last);
        int y = get(s, x[i]) - dist;
        if (get(s, last) > y) {
            int l = discrete_binary_search(last, -INF, [&](int k) { return get(s, k) >= y + abs(k - last); });
            int r = discrete_binary_search(last, INF, [&](int k) { return get(s, k) >= y + abs(k - last); });
            auto pl = s.lower_bound({l, -INF}), pr = s.lower_bound({r + 1, -INF});
            s.erase(pl, pr);
            s.emplace(l, y + abs(l - last));
            s.emplace(last, y);
            s.emplace(r, y + abs(r - last));
        }
        bias += dist;
        last = x[i];
    }
    int ans = 0;
    for (auto p:s) { chmin(ans, p.second); }
    ans += bias;
    cout << ans << endl;
}


Measured memory_bytes: 5208