//#define _GLIBCXX_DEBUG

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

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>
bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>
bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>
void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>
void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++)
{for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>
void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];
for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>
vector<vector<T>>vec(ll x, ll y, T w){
  vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};
vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>
vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v(ts...))>(a,make_v(ts...));
}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2>&p){
  return os << p.first << " " << p.second;
}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
template< typename Monoid, typename OperatorMonoid,typename F, typename G, typename H>
struct LazySegmentTree {
  ll sz, height, n;
  vector< Monoid > data;
  vector< OperatorMonoid > lazy;
  const F f;
  const G g;
  const H h;
  Monoid M1;
  OperatorMonoid OM0;
  LazySegmentTree(ll n, const F &f,const G &g, const H &h, Monoid M1, OperatorMonoid OM0):n(n),f(f),g(g),h(h),M1(M1),OM0(OM0){
    sz = 1;
    height = 0;
    while(sz < n) sz <<= 1, height++;
    data.assign(2 * sz, M1);
    lazy.assign(2 * sz, OM0);
  }

  void set(ll k, const Monoid &x) {
    data[k + sz] = x;
  }

  void build() {
    for(ll k = sz - 1; k > 0; k--) {
      data[k] = f(data[2 * k + 0], data[2 * k + 1]);
    }
  }

  inline void propagate(ll k) {
    if(lazy[k] != OM0) {
      lazy[2 * k + 0] = h(lazy[2 * k + 0], lazy[k]);
      lazy[2 * k + 1] = h(lazy[2 * k + 1], lazy[k]);
      data[k] = reflect(k);
      lazy[k] = OM0;
    }
  }

  inline Monoid reflect(ll k) {
    return lazy[k] == OM0 ? data[k] : g(data[k], lazy[k]);
  }

  inline void recalc(ll k) {
    while(k >>= 1) data[k] = f(reflect(2 * k + 0), reflect(2 * k + 1));
  }

  inline void thrust(ll k) {
    for(ll i = height; i > 0; i--) propagate(k >> i);
  }

  void update(ll a, ll b, const OperatorMonoid &x) {
	if(a>=b)return;
    thrust(a += sz);
    thrust(b += sz - 1);
    for(ll l = a, r = b + 1; l < r; l >>= 1, r >>= 1) {
      if(l & 1) lazy[l] = h(lazy[l], x), ++l;
      if(r & 1) --r, lazy[r] = h(lazy[r], x);
    }
    recalc(a);
    recalc(b);
  }

  Monoid query(ll a, ll b) {
    thrust(a += sz);
    thrust(b += sz - 1);
    Monoid L = M1, R = M1;
    for(ll l = a, r = b + 1; l < r; l >>= 1, r >>= 1) {
      if(l & 1) L = f(L, reflect(l++));
      if(r & 1) R = f(reflect(--r), R);
    }
    return f(L, R);
  }

  Monoid operator[](const ll &k) {
    return query(k, k + 1);
  }

  template< typename C >
  ll find_subtree(ll a, const C &check, Monoid &M, bool type) {
    while(a < sz) {
      propagate(a);
      Monoid nxt = type ? f(reflect(2 * a + type), M) : f(M, reflect(2 * a + type));
      if(check(nxt)) a = 2 * a + type;
      else M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }

  template< typename C >
  ll find_first(ll a, const C &check) {
    Monoid L = M1;
    if(a <= 0) {
      if(check(f(L, reflect(1)))) return find_subtree(1, check, L, false);
      return -1;
    }
    thrust(a + sz);
    ll b = sz;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) {
        Monoid nxt = f(L, reflect(a));
        if(check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }


  template< typename C >
  ll find_last(ll b, const C &check) {
    Monoid R = M1;
    if(b >= sz) {
      if(check(f(reflect(1), R))) return find_subtree(1, check, R, true);
      return -1;
    }
    thrust(b + sz - 1);
    ll a = sz;
    for(b += sz; a < b; a >>= 1, b >>= 1) {
      if(b & 1) {
        Monoid nxt = f(reflect(--b), R);
        if(check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
  void print(){
    for(ll i=0;i<n;i++)if((*this)[i])cout<<"x|";else cout<<(*this)[i]<<"|";
    cout<<endl;
  }
};

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  auto f=[&](ll x,ll y){
    return min(x,y);
  };
  auto g=[&](ll x,ll y){
    return x+y;
  };
  auto h=[&](ll x,ll y){
    return x+y;
  };
  ll n,q,a,b;cin>>n>>q>>a>>b;a--;b--;
  using LS=LazySegmentTree<ll,ll,decltype(f),decltype(g),decltype(h)>;
  LS seg1(n,f,g,h,2*INF,0);
  LS seg2(n,f,g,h,2*INF,0);
  vector<ll>x(q+1);
  rep(i,0,q)cin>>x[i+1],x[i+1]--;
  x[0]=b;
  rep(i,0,n)seg1.set(i,INF);
  rep(i,0,n)seg2.set(i,INF);
  seg1.set(a,a);
  seg2.set(a,n-a-1);
  seg1.build();seg2.build();
  auto ch=[&](ll x,ll idx,auto &seg){
    auto v=seg[idx];
    //cout<<x spa v spa idx<<endl;
    if(x<v)seg.update(idx,idx+1,x-v);
  };
  auto prints=[&]{
    rep(i,0,n)if(seg1[i]<=INF-10000)cout<<seg1[i]-i<<" ";else cout<<"x ";cout<<endl;
    rep(i,0,n)if(seg2[i]<=INF-10000)cout<<seg2[i]-(n-i-1)<<" ";else cout<<"x ";cout<<endl;
  };
  //prints();
  rep(i,0,q){
    ll upd=INF;
    //保持している値を変える場合
    chmin(upd,seg2.query(0,x[i+1]+1)-(n-x[i+1]-1));
    chmin(upd,seg1.query(x[i+1],n)-(x[i+1]));
    seg1.update(0,n,abs(x[i+1]-x[i]));
    seg2.update(0,n,abs(x[i+1]-x[i]));
    //cout<<upd<<endl;
    ch(upd+x[i],x[i],seg1);
    ch(upd+(n-x[i]-1),x[i],seg2);
    //cout<<x[i] spa x[i+1]<<endl;
    //prints();
  }
  res=INF;
  rep(i,0,n){
    chmin(res,seg1[i]-i);
    chmin(res,seg2[i]-(n-i-1));
  }
  cout<<res<<endl;
  return 0;
}

Measured memory_bytes: 21156